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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Gri: About draw commands</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"></head>
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<!-- newfile Draw.html "Gri: About draw commands" "Gri Commands" --> 

<!-- @node   Draw, Draw Arc, Differentiate, List Of Gri Commands -->
<a name="Draw" ></a>

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<tr>
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<font size=-1>
<br>
Chapters:
<br>
&nbsp;&nbsp;<a href="Introduction.html">1: Introduction</a><br>
&nbsp;&nbsp;<a href="SimpleExample.html">2: Simple example</a><br>
&nbsp;&nbsp;<a href="InvokingGri.html">3: Invocation</a><br>
&nbsp;&nbsp;<a href="GettingMoreControl.html">4: Finer Control</a><br>
&nbsp;&nbsp;<a href="X-Y.html">5: X-Y Plots</a><br>
&nbsp;&nbsp;<a href="ContourPlots.html">6: Contour Plots</a><br>
&nbsp;&nbsp;<a href="Images.html">7: Image Plots</a><br>
&nbsp;&nbsp;<a href="Examples.html">8: Examples</a><br>
&nbsp;&nbsp;<a href="Commands.html">9: Gri Commands</a><br>
&nbsp;&nbsp;<a href="Programming.html">10: Programming</a><br>
&nbsp;&nbsp;<a href="Environment.html">11: Environment</a><br>
&nbsp;&nbsp;<a href="Emacs.html">12: Emacs Mode</a><br>
&nbsp;&nbsp;<a href="History.html">13: History</a><br>
&nbsp;&nbsp;<a href="Installation.html">14: Installation</a><br>
&nbsp;&nbsp;<a href="Bugs.html">15: Gri Bugs</a><br>
&nbsp;&nbsp;<a href="TestSuite.html">16: Test Suite</a><br>
&nbsp;&nbsp;<a href="GriInThePress.html">17: Gri in Press</a><br>
&nbsp;&nbsp;<a href="Acknowledgments.html">18: Acknowledgments</a><br>
&nbsp;&nbsp;<a href="License.html">19: License</a><br>
<br>
Indices:<br>
&nbsp;&nbsp;<a href="ConceptIndex.html"><i>Concepts</i></a><br>
&nbsp;&nbsp;<a href="CommandIndex.html"><i>Commands</i></a><br>
&nbsp;&nbsp;<a href="BuiltinIndex.html"><i>Variables</i></a><br>
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<area alt="Gri: `differentiate' command" shape="rect" coords="557,2,573,24" href="Differentiate.html">
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<h3>9.3.9: The `<font color="#82140F"><code>draw</code></font>' commands</h3>

<!-- latex: \index{draw} -->
Draw commands do actual drawing on the page.  You can draw axes,
lineplots, symbols, contours, images, and text.  
<p>
<b>NOTE</b> Gri likes drawings to have axes, so if a `<font color="#82140F"><code>draw</code></font>' command
is executed before any axes have been drawn, Gri will draw axes after it
draws the item.  (You can get drawings without axes by preceding any
other `<font color="#82140F"><code>draw</code></font>' commands with the command `<font color="#82140F"><code>draw axes none</code></font>'.)
Many users have been surprised by the results of this rule.  For
example, if you do `<font color="#82140F"><code>set graylevel 0.5</code></font>' before `<font color="#82140F"><code>draw curve</code></font>',
you'll find that the axes are drawn in gray also.  To avoid this, make
sure to do `<font color="#82140F"><code>draw axes</code></font>' before you modify the graylevel.)
<p>
<UL>
<LI><a href="Draw.html#DrawArc">Draw Arc</a>: Draw an arc segment
<LI><a href="Draw.html#DrawArrow">Draw Arrow</a>: Draw single arrow
<LI><a href="Draw.html#DrawArrows">Draw Arrows</a>: Draw many arrows (using columns)
<LI><a href="Draw.html#DrawAxesIfNeeded">Draw Axes If Needed</a>: Draw axes if haven't done so yet
<LI><a href="Draw.html#DrawAxes">Draw Axes</a>: Draw axes
<LI><a href="Draw.html#DrawBorderBox">Draw Border Box</a>: Draw border around plot
<LI><a href="Draw.html#DrawBox">Draw Box</a>: Draw a box, possibly filled
<LI><a href="Draw.html#DrawCircle">Draw Circle</a>: Draw a circle
<LI><a href="Draw.html#DrawContour">Draw Contour</a>: Draw contour(s)
<LI><a href="Draw.html#DrawCurve">Draw Curve</a>: Draw a curve of y(x) column data
<LI><a href="Draw.html#DrawEssay">Draw Essay</a>: Draw text, adjusting position for each line
<LI><a href="Draw.html#DrawGriLogo">Draw Gri Logo</a>: Draw a Gri logo
<LI><a href="Draw.html#DrawGrid">Draw Grid</a>: Draw the location of grid points
<LI><a href="Draw.html#DrawImageHistogram">Draw Image Histogram</a>: Draw histogram of values in image
<LI><a href="Draw.html#DrawImagePalette">Draw Image Palette</a>: Draw palette used in image plots
<LI><a href="Draw.html#DrawImage">Draw Image</a>: Draw image
<LI><a href="Draw.html#DrawIsopycnal">Draw Isopycnal</a>: Draw isopycnal line on TS plot
<LI><a href="Draw.html#DrawIsospice">Draw Isospice</a>: Draw iso-spice line on TS plot
<LI><a href="Draw.html#DrawLabelBoxed">Draw Label Boxed</a>: Draw a label in a box
<LI><a href="Draw.html#DrawLabelWhiteunder">Draw Label Whiteunder</a>: Draw a label with white ink under it
<LI><a href="Draw.html#DrawLabelForLastCurve">Draw Label For Last Curve</a>: What it says
<LI><a href="Draw.html#DrawLabel">Draw Label</a>: Draw text somewhere
<LI><a href="Draw.html#DrawLineFrom">Draw Line From</a>: Draw line segment
<LI><a href="Draw.html#DrawLineLegend">Draw Line Legend</a>: Draw legend displaying line types
<LI><a href="Draw.html#DrawLines">Draw Lines</a>: Draw sequence of parallel lines
<LI><a href="Draw.html#DrawPatches">Draw Patches</a>: Draw grayscale patches showing z(x,y)
<LI><a href="Draw.html#DrawPolygon">Draw Polygon</a>: Draw a polygon
<LI><a href="Draw.html#DrawRegressionLine">Draw Regression Line</a>: Draw line from regression between x and y
<LI><a href="Draw.html#DrawSymbolAt">Draw Symbol At</a>: Draw a symbol at a point
<LI><a href="Draw.html#DrawSymbolLegend">Draw Symbol Legend</a>: Draw a symbol and a string describing it
<LI><a href="Draw.html#DrawSymbol">Draw Symbol</a>: Draw symbols at (x,y), or at a point
<LI><a href="Draw.html#DrawTimeStamp">Draw Time Stamp</a>: Draw a timestamp at top of plot
<LI><a href="Draw.html#DrawTitle">Draw Title</a>: Draw a title for plot
<LI><a href="Draw.html#DrawValues">Draw Values</a>: Draw numbers beside z(x,y)
<LI><a href="Draw.html#DrawXAxis">Draw X Axis</a>: Draw the x axis
<LI><a href="Draw.html#DrawXBoxPlot">Draw X Box Plot</a>: Draw box plots showing x spread
<LI><a href="Draw.html#DrawYAxis">Draw Y Axis</a>: Draw the y axis
<LI><a href="Draw.html#DrawYBoxPlot">Draw Y Box Plot</a>: Draw box plots showing y spread
<LI><a href="Draw.html#DrawZeroLine">Draw Zero Line</a>: Draw y=0 or x=0
</UL>

<!-- @node   Draw Arc, Draw Arrow, Draw, Draw -->
<a name="DrawArc" ></a>
<h4>9.3.9.1: The `<font color="#82140F"><code>draw arc</code></font>' command</h4>

<!-- latex: \index{draw arc} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw arc [filled] .xc_cm. .yc_cm. .r_cm. .angle_1. .angle_2.'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
Draw an "arc", that is, a portion of a circle.  The center of the
circle is at the coordinate (`<font color="#82140F"><code>.xc_cm.</code></font>', `<font color="#82140F"><code>.yc_cm.</code></font>'), and the
circle radius is `<font color="#82140F"><code>.r_cm.</code></font>', all three quantities being in cm on
the page, <em>not</em> in user-units.  The arc starts at angle
`<font color="#82140F"><code>.angle_1.</code></font>', measured in degrees counterclockwise from a
horizontal line, and extends to angle `<font color="#82140F"><code>.angle_2.</code></font>', in the same
units.
<p>
If the keyword `<font color="#82140F"><code>filled</code></font>' is present, the arc is filled with the
current color.  Otherwise it is drawn with the current "curve"
linewidth see <a href="Set.html#SetLineWidth">Set Line Width</a>.
<p>
<!-- @node   Draw Arrow, Draw Arrows, Draw Arc, Draw -->
<a name="DrawArrow" ></a>
<h4>9.3.9.2: `<font color="#82140F"><code>draw arrow</code></font>'</h4>


<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw arrow from .x0. .y0. to .x1. .y1. [cm]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
With no optional parameters, draw an arrow from (`<font color="#82140F"><code>.x0.</code></font>',
`<font color="#82140F"><code>.y0.</code></font>') to (`<font color="#82140F"><code>.x1.</code></font>', `<font color="#82140F"><code>.y1.</code></font>'), where coordinates are in
user units.  The arrow head will be at (`<font color="#82140F"><code>.x1.</code></font>', `<font color="#82140F"><code>.y1.</code></font>'), and
its size is as set by most recent call to `<font color="#82140F"><code>set arrow size</code></font>'.  With
the `<font color="#82140F"><code>cm</code></font>' keyword present, the coordinates are in centimetres on the
page.  NOTE: This will not cause auto-drawing of axes.
<p>
<!-- @node   Draw Arrows, Draw Axes If Needed, Draw Arrow, Draw -->
<a name="DrawArrows" ></a>
<h4>9.3.9.3: `<font color="#82140F"><code>draw arrows</code></font>'</h4>

<!-- latex: \index{draw arrows} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw arrows'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a vector field consisting of arrows emanating from the coordinates
stored in the (x, y) columns.  The lengths and orientations of the
arrows are stored in the (u, v) columns, and the scale for the (u,v)
columns is set by `<font color="#82140F"><code>set u scale</code></font>' and `<font color="#82140F"><code>set v scale</code></font>'.  <b>See also</b>
(1) To set arrow size, use `<font color="#82140F"><code>set arrow size</code></font>'.  (2) To get a single
arrow, use `<font color="#82140F"><code>draw arrow</code></font>'.
<p>

<!-- @node   Draw Axes If Needed, Draw Axes, Draw Arrows, Draw -->
<a name="DrawAxesIfNeeded" ></a>
<!-- latex: \index{draw axes if needed} -->
<h4>9.3.9.4: `<font color="#82140F"><code>draw axes if needed</code></font>'</h4>


<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw axes if needed'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw axes frame if required.  Used within gri commands that auto-draw axes.
NOTE: this should only be done by developers.
<p>


<!-- @node   Draw Axes, Draw Border Box, Draw Axes If Needed, Draw -->
<a name="DrawAxes" ></a>
<!-- latex: \index{draw axes} -->
<h4>9.3.9.5: `<font color="#82140F"><code>draw axes</code></font>'</h4>


<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw axes [.style.|frame|none]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With no style (`<font color="#82140F"><code>.style.</code></font>') specified, draw x-y axes frame labelled
at left and bottom. The value of `<font color="#82140F"><code>.style.</code></font>' determines the style of
axes: 
<ul>
<p>
<li> `<font color="#82140F"><code>.style. = 0</code></font>'
Draw x-y axes frame labelled at left and bottom.  Since this is the
default, it's best to leave it out altogether to make your code easier to
understand.
<p>
<li> `<font color="#82140F"><code>.style. = 1</code></font>'
Draw axes without tics at top and right
<p>
<li> `<font color="#82140F"><code>.style. = 2</code></font>'
Draw axes frame with no tics or labels; same as `<font color="#82140F"><code>draw axes frame</code></font>'
</ul>
<p>
With the keyword `<font color="#82140F"><code>frame</code></font>' specified, draw axes frame with no tics or
labels (just like `<font color="#82140F"><code>.style.</code></font>' = 2, but preferable because it makes for
code that is easier to read and understand).
<p>
With the keyword `<font color="#82140F"><code>none</code></font>' specified, prevent Gri from automatically
drawing axes when drawing curves.
<p>
Note: `<font color="#82140F"><code>set axes style</code></font>' can also be used to set axes properties,
and then simply using `<font color="#82140F"><code>draw axes</code></font>', or letting axes be auto-drawn,
will result in the desired effect (see <a href="Set.html#SetAxesStyle">Set Axes Style</a>).  However, if
the `<font color="#82140F"><code>draw axes</code></font>' command explicitly asks for a particular style,
then it over-rides the style set by `<font color="#82140F"><code>Set Axes Style</code></font>'.
<p>

<!-- @node   Draw Border Box, Draw Box, Draw Axes, Draw -->
<a name="DrawBorderBox" ></a>
<!-- latex: \index{draw border box} -->
<h4>9.3.9.6: `<font color="#82140F"><code>draw border box</code></font>'</h4>


<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw border box .xleft. .ybottom. .xright. .ytop. \
    .width_cm. .brightness.'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw gray box, as decoration or alignment key for pastup. The box, with
outer lower left corner at (`<font color="#82140F"><code>.xleft.</code></font>', `<font color="#82140F"><code>.ybottom.</code></font>') and outer
upper right corner at (`<font color="#82140F"><code>.xright</code></font>'., `<font color="#82140F"><code>.ytop.</code></font>') -- both coordinates
being in centimetres on the page -- is drawn with thickness
`<font color="#82140F"><code>.width_cm.</code></font>' and with graylevel `<font color="#82140F"><code>.brightness.</code></font>' (0 for black; 1
for white).  The gray line is drawn inside the box.  After drawing the
gray line, a thin black line is drawn along the outside edge.
<p>
If the geometry is not specified with `<font color="#82140F"><code>.xleft.</code></font>' and the other
parameters, then a reasonable margin is used around the present axes
area, and the defaults (`<font color="#82140F"><code>.border.</code></font>' = 0.2, `<font color="#82140F"><code>.brightness.</code></font>' =
0.75) are used.
<p>
NOTE: This command does not cause auto-drawing of axes.
<p>

<!-- @node   Draw Box, Draw Circle, Draw Border Box, Draw -->
<a name="DrawBox" ></a>
<h4>9.3.9.7: `<font color="#82140F"><code>draw box</code></font>'</h4>

<!-- latex: \index{draw box} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw box filled .xleft. .ybottom. .xright. .ytop. [cm|pt]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
 
Draw filled box spanning indicated range, with lower-left corner at
(`<font color="#82140F"><code>.xleft.</code></font>', `<font color="#82140F"><code>.ybottom.</code></font>') and upper-right corner at
(`<font color="#82140F"><code>.xright.</code></font>', `<font color="#82140F"><code>.ytop.</code></font>').  The corners are specified in user
coordinates, unless the optional `<font color="#82140F"><code>cm</code></font>' or `<font color="#82140F"><code>pt</code></font>' keyword is
present, in which case they are in centimetres or points on the page.
An error will result if you specify user coordinates but they aren't
defined yet.
<p>
No checking is done on the rectangle; for example, there is no
requirement that `<font color="#82140F"><code>.xleft.</code></font>' be to the left of `<font color="#82140F"><code>.xright.</code></font>' in your
coordinate system.
<p>
NOTE: if the box is specified in user units, this command will cause
auto-drawing of axes, but not if the box is specified in `<font color="#82140F"><code>cm</code></font>'
or `<font color="#82140F"><code>pt</code></font>' units
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw box .xleft. .ybottom. .xright. .ytop. [cm|pt]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw box spanning indicated range, with lower-left corner at
(`<font color="#82140F"><code>.xleft.</code></font>', `<font color="#82140F"><code>.ybottom.)</code></font>' and upper-right corner at (`<font color="#82140F"><code>.xright.</code></font>',
`<font color="#82140F"><code>.ytop.</code></font>').
<p>
The corners are specified in user coordinates, unless the optional
`<font color="#82140F"><code>cm</code></font>' or `<font color="#82140F"><code>pt</code></font>' keyword is present, in which case they are in
centimetres or points on the page.  An error will result if you
specify user coordinates but they aren't defined yet.
<p>
No checking is done on the rectangle; for example, there is no
requirement that `<font color="#82140F"><code>.xleft.</code></font>' be to the left of `<font color="#82140F"><code>.xright.</code></font>' in your
coordinate system.
<p>

<!-- @node   Draw Circle, Draw Contour, Draw Box, Draw -->
<a name="DrawCircle" ></a>
<h4>9.3.9.8: `<font color="#82140F"><code>draw circle</code></font>'</h4>

<!-- latex: \index{draw circle} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw circle with radius .r_cm. at .x_cm. .y_cm.
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw circle of specified radius (in cm) at the specified
location (in cm on the page).
<p>

<!-- @node   Draw Contour, Draw Curve, Draw Circle, Draw -->
<a name="DrawContour" ></a>
<h4>9.3.9.9: `<font color="#82140F"><code>draw contour</code></font>'</h4>

<!-- latex: \index{draw contour} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw contour [{.value. \
  [unlabelled | {labelled "\label"}]} \
  | {.min. .max. .inc. \
    [.inc_unlabelled.] [unlabelled]}]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

This command draws contours based on the "grid" data previously read in
by a `<font color="#82140F"><code>read grid data</code></font>' command or created by gridding column data
with a `<font color="#82140F"><code>create grid from columns</code></font>' command.  If the grid data don't
exist, or if the x and y locations of the grid points do not exist (see
`<font color="#82140F"><code>set x grid</code></font>', `<font color="#82140F"><code>set y grid</code></font>', etc), Gri will complain.
<p>
With no optional parameters, draw labelled contours at an interval
that is picked automatically based on the range of the data.
     
With a single numerical value (`<font color="#82140F"><code>.value.</code></font>'), draw the indicated
contour.  With the addition of `<font color="#82140F"><code>labelled "\label"</code></font>', put the
indicated label instead of a numeric label.  This can be useful for
using scientific notation instead of computer notation for exponents,
e.g.  `<font color="#82140F"><code>draw contour 1e-5 labelled "10$^{-5}$"</code></font>'.
<p>
With (`<font color="#82140F"><code>.min.</code></font>', `<font color="#82140F"><code>.max.</code></font>' and `<font color="#82140F"><code>.inc.</code></font>') given, draw
contours for z(x,y) = `<font color="#82140F"><code>.min.</code></font>', z(x,y) = `<font color="#82140F"><code>.min. + .inc.</code></font>',
z(x,y) = `<font color="#82140F"><code>.min. + 2*.inc.</code></font>', ..., z(x,y) = `<font color="#82140F"><code>.max.</code></font>'
<p>
With the additional value `<font color="#82140F"><code>.inc_unlabelled.</code></font>' specified, extra
unlabelled contours are drawn at this finer interval.
<p>
With the optional parameter `<font color="#82140F"><code>unlabelled</code></font>' at the end of any form
of this command (except the `<font color="#82140F"><code>labelled "\label"</code></font>' variation, of
course), Gri will not label the contour(s).
<p>
<b>Hint:</b> It can be effective to draw contours at a certain interval
with labels, and a thicker pen, e.g.
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
set line width rapidograph 3x0
draw contour -2 5 1 0.25
set line width rapidograph 1
draw contour -2 5 1
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
<b>Interpolation method:</b> The interpolation scheme is the same used for
converting grid-values to image values (see <a href="Convert.html#ConvertGridToImage">Convert Grid To Image</a>).
<p>
<b>See also</b> `<font color="#82140F"><code>set contour labels</code></font>'
<p>

<!-- @node   Draw Curve, Draw Essay, Draw Contour, Draw -->
<a name="DrawCurve" ></a>
<h4>9.3.9.10: `<font color="#82140F"><code>draw curve</code></font>'</h4>

<!-- latex: \index{draw curve} -->
Several forms exist.
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw curve'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draws a curve connecting the points (x,y), which have been read in by a
command like `<font color="#82140F"><code>read columns x y</code></font>'.  Line segments are drawn between
all (x,y) points, except: (1) no line segments are drawn to any missing
data (see `<font color="#82140F"><code>set missing value</code></font>'), and (2) if clipping is turned on
(see `<font color="#82140F"><code>set clip on</code></font>'), no line segments are drawn outside the
clipping region.  <b>See also</b> `<font color="#82140F"><code>draw curve overlying</code></font>'
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw curve overlying'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Like `<font color="#82140F"><code>draw curve</code></font>', except that before drawing, the area underneath
the curve (+/- one linewidth) is whited out.  This clarifies graphs
where curves overlie other curves or the axes.  
<b>See also</b> `<font color="#82140F"><code>draw curve</code></font>'.
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw curve filled [to {.y. y}|{.x. x}]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

The form `<font color="#82140F"><code>draw curve filled ...</code></font>' draws filled curves.  If the
`<font color="#82140F"><code>to .value.</code></font>' is not specified, fill the region defined by the x-y points
using the current paint colour (see `<font color="#82140F"><code>set graylevel</code></font>').  To complete
the shape, an extra line is drawn between the first and last points.
<p>
The form `<font color="#82140F"><code>draw curve filled to .y. y</code></font>' fills the region between y(x)
and y = `<font color="#82140F"><code>.y.</code></font>'; do not connect the first and last points as in the
case where `<font color="#82140F"><code>to .yvalue.</code></font>' is not specified.
<p>
The form `<font color="#82140F"><code>draw curve filled to .x. x</code></font>' fills the region between x(y)
and x = `<font color="#82140F"><code>.x.</code></font>'
<p>




<!-- @node   Draw Essay, Draw Gri Logo, Draw Curve, Draw -->
<a name="DrawEssay" ></a>
<h4>9.3.9.11: `<font color="#82140F"><code>draw essay</code></font>'</h4>

<!-- latex: \index{draw essay} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw essay "text"|reset'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw indicated text on the page.  Succeeding calls draw text further and
further down the page, starting at the top.
<p>
The current font size is used; to alter this, use `<font color="#82140F"><code>set font size</code></font>'
before `<font color="#82140F"><code>draw essay</code></font>'.
<p>
When `<font color="#82140F"><code>reset</code></font>' is present instead of text, the drawing position is
reset to the top of the page.  Use this after a `<font color="#82140F"><code>new page</code></font>' command
to ensure that the next text lines will appear at the top of the page as
expected.  EXAMPLE:
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
set font size 2 cm
draw essay "Line 1, at top of page"
draw essay "Line 2, below top line"
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

<!-- @node   Draw Gri Logo, Draw Grid, Draw Essay, Draw -->
<a name="DrawGriLogo" ></a>
<h4>9.3.9.12: `<font color="#82140F"><code>draw gri logo</code></font>'</h4>

<!-- latex: \index{draw gri logo} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw gri logo .x_cm. .y_cm. .height_cm. .style. \fgcolor \bgcolor'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a Gri logo at given location with given style and colors.  The
lower-left corner of the logo will be `<font color="#82140F"><code>.x_cm.</code></font>' centimeters from the
left-hand side of the page and `<font color="#82140F"><code>.y_cm.</code></font>' centimeters from the bottom
of the page.  The logo will be `<font color="#82140F"><code>.height_cm.</code></font>' centimeters tall.  The
textual parameters `<font color="#82140F"><code>\fgcolor</code></font>' and `<font color="#82140F"><code>\bgcolor</code></font>' give the foreground and
background colors, respectively, and these are used in styles as noted
in the table below
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
.style.    style
=======    ===================
   0       stroke curve
   1       fill with color \fgcolor, no background
   2       fill with color \fgcolor it in tight box of color \bgcolor
   3       as 2 but in square box
   4       draw in \fgcolor on top of shifted copy in \bgcolor
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
An example is given below
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw gri logo 1 1 3 4 blue green
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
<!-- @node   Draw Grid, Draw Image Histogram, Draw Gri Logo, Draw -->
<a name="DrawGrid" ></a>
<h4>9.3.9.13: `<font color="#82140F"><code>draw grid</code></font>'</h4>

<!-- latex: \index{draw grid} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw grid'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw plus-signs at locations where grid data are non-missing.
<p>
<!-- @node   Draw Image Histogram, Draw Image Palette, Draw Grid, Draw -->
<a name="DrawImageHistogram" ></a>
<h4>9.3.9.14: `<font color="#82140F"><code>draw image histogram</code></font>'</h4>

<!-- latex: \index{draw image histogram} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw image histogram \
  [box .llx_cm. .lly_cm. .urx_cm. .ury_cm.]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With no optional parameters, draw histogram of all unmasked parts of the
image, placing it above the current top of the plot.
<p>
When the `<font color="#82140F"><code>box</code></font>' options are present, they specify the box (in
centimetre coordinates on the page) in which the histogram plot is to be
done.
<p>


<!-- @node   Draw Image Palette, Draw Image, Draw Image Histogram, Draw -->
<a name="DrawImagePalette" ></a>
<h4>9.3.9.15: `<font color="#82140F"><code>draw image palette</code></font>'</h4>

<!-- latex: \index{draw image palette} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw image palette 
   [axisleft|axisright|axistop|axisbottom] 
   [left .left. right .right. [increment .inc.]] 
   [box .xleft_cm. .ybottom_cm. .xright_cm. .ytop_cm.]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With no optional parameters, draw palette for image, placed above the
current top showing values ranging from `<font color="#82140F"><code>.min_value.</code></font>' to
`<font color="#82140F"><code>.max_value.</code></font>' as given in `<font color="#82140F"><code>set image range</code></font>'.
<p>
Optional keywords (`<font color="#82140F"><code>axisleft</code></font>', etc) control the orientation of the
palette, the default being `<font color="#82140F"><code>axisbottom</code></font>'.
<p>
The optional parameters `<font color="#82140F"><code>.left.</code></font>' and `<font color="#82140F"><code>.right.</code></font>' may be used to
specify the range to be drawn in the palette.  If the additional
optional parameter `<font color="#82140F"><code>.inc.</code></font>' is present, it specifies the interval
between tics on the scale; if not present, the tics are at increments of
2 * (`<font color="#82140F"><code>.right.</code></font>' - `<font color="#82140F"><code>.left</code></font>'.).  (If `<font color="#82140F"><code>.inc.</code></font>'  has the wrong
sign, it will be corrected without warning.)
<p>
When the optional `<font color="#82140F"><code>box</code></font>' parameters are present, they prescribe the
bounding box to contain the palette.  The units are centimetres on the
page.  If these parameters are not present, the box will be drawn above
the image plot.
<p>
<b>Hint</b> It is a good idea to make the palette range `<font color="#82140F"><code>.left.</code></font>' to
`<font color="#82140F"><code>.right.</code></font>' extend a little beyond the range of full white and full
black, since otherwise neither pure white nor pure black will appear in
the colorbar.  For example
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
set image grayscale black 0 white 1 increment 0.1
draw image palette left -0.1 right 1.1 increment 0.1
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
<b>Hint</b> Continuous-tone images with superimposed contours are often
effective.  To get the contour lines drawn on the image palette, do
something like this
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw image
.left.   = 0
.right.  = 9
.inc.    = 1
.space.  = 3
.height. = 1
draw image palette left .left. \
  right .right. \
  increment .inc. \
  box \
    ..xmargin.. \
    {rpn ..ymargin.. ..ysize.. + .space. + } \
    {rpn ..xmargin.. ..xsize.. +} \
    {rpn ..ymargin.. ..ysize.. + .space. + .height. + }
draw contour .left. .right. .inc. unlabelled
<p>
.c. = .left.
while {rpn .right. .c. &lt;= }
  .c_cm. = {rpn .c. .left. - \
   .right. .left. - / \
    ..xsize.. * ..xmargin.. +}
  draw line from \
    .c_cm. \
    {rpn ..ymargin.. ..ysize.. + .space. + }\
    to \
    .c_cm. \
    {rpn ..ymargin.. ..ysize.. + .space. + .height. +} \
    cm
  .c. += 1
end while
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

<!-- @node   Draw Image, Draw Isopycnal, Draw Image Palette, Draw -->
<a name="DrawImage" ></a>
<h4>9.3.9.16: `<font color="#82140F"><code>draw image</code></font>'</h4>

<!-- latex: \index{draw image} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw image'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw black/white image made by `<font color="#82140F"><code>convert grid to image</code></font>' or by
`<font color="#82140F"><code>read image</code></font>'.
<p>

<!-- @node   Draw Isopycnal, Draw Isospice, Draw Image, Draw -->
<a name="DrawIsopycnal" ></a>
<h4>9.3.9.17: `<font color="#82140F"><code>draw isopycnal</code></font>'</h4>

<!-- latex: \index{draw isopycnal} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw isopycnal \
   [unlabelled] .density. [.P_sigma. [.P_theta.]]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>
Draw isopycnal curve for a temperature-salinity diagram.  This curve is
the locus of temperature and salinity values which yield seawater of the
indicated density, at the indicated pressure.  The UNESCO equation of
state is used.
<p>
For the results to make sense, the x-axis should be salinity and the
y-axis should be either in-situ temperature or potential temperature.
<p>
The `<font color="#82140F"><code>.density.</code></font>' unit is kg/m^3.  If the supplied value exceeds 100
then it will be taken to indicate the actual density; otherwise it will
be taken to indicate density minus 1000 kg/m^3.  (The deciding value of
100 kg/m^3 was chosen since water never has this density; the more
intuitive value of 1000 kg/m^3 would be inappropriate since water can
have that density at some temperatures.)  Thus, 1020 and 20 each
correspond to an actual density of 1020 kg/m^3.
<p>
The reference pressure for density, `<font color="#82140F"><code>.P_sigma.</code></font>', is in decibars
(roughly corresponding to meters of water depth).  If no value is
supplied, a pressure of 0 dbar (i.e. atmospheric pressure) is used.
<p>
The reference pressure for theta, `<font color="#82140F"><code>.P_theta.</code></font>', is in decibars, and
defaults to zero (i.e. atmospheric pressure) if not supplied.  This
option is used if the y-axis is potential temperature referenced to a
pressure other than the surface.  Normally the potential temperature is,
however, referenced to the surface, so that specifying a value for
`<font color="#82140F"><code>.P_theta.</code></font>' is uncommon.
<p>
By default, labels will be drawn on the isopycnal curve; this may be
prevented by supplying the keyword `<font color="#82140F"><code>unlabelled</code></font>'.  If labels are
drawn, they will be of order 1000, or of order 10 to 30, according to
the value of `<font color="#82140F"><code>.density.</code></font>' supplied (see above).  The label format
defaults to "%g" in the C-language format notation, and may be
controlled by `<font color="#82140F"><code>set contour format</code></font>'.  The label position may be
controlled by `<font color="#82140F"><code>set contour label position</code></font>' command (bug: only
non-centered style works).  Setting label position is useful if labels
collide with data points.  Labels are drawn in the whiteunder mode, so
they can white-out data below.  For this reason it is common to draw
data points after drawing isopycnals.
<p>
If the y-axis is in-situ temperature, the command should be called
without specifying `<font color="#82140F"><code>.P_sigma.</code></font>', or, equivalently, with
`<font color="#82140F"><code>.P_sigma.</code></font>' = 0.  That is, the resultant curve will
correspond to the (S,T) solution to the equation
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
.density. = RHO(S, T, 0)
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

where `<font color="#82140F"><code>RHO=RHO(S,T,p)</code></font>' is the UNESCO equation of state for
seawater.  This is a curve of constant sigma_T.
<p>
If the y-axis is potential temperature referenced to the surface,
`<font color="#82140F"><code>.P_theta.</code></font>' should not be specified, or should be specified to be
zero.  The resultant curve corresponds to a constant value of
potential density referenced to pressure `<font color="#82140F"><code>.P_sigma.</code></font>', i.e. the
(S,theta) solution to the equation
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
.density. = RHO(S, theta, .P_sigma.)
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

For example, with `<font color="#82140F"><code>.P_sigma.=0</code></font>' (the default), the result
is a curve of constant sigma_theta.
<p>
If the y-axis is potential temperature referenced to some pressure other
than that at the surface, `<font color="#82140F"><code>.P_theta.</code></font>' should be supplied.  The
resultant curve will be the (S,theta) solution to the equation
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
.density. = RHO(S, T', .P_sigma.)
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

where
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
T'=THETA(S, theta, .P_theta., .P_sigma.)
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

where `<font color="#82140F"><code>THETA=THETA(S,T,P,Pref)</code></font>' is the UNESCO formula for potential
temperature of a water-parcel moved to a reference pressure of
`<font color="#82140F"><code>Pref</code></font>'.  Note that `<font color="#82140F"><code>theta</code></font>', potential temperature referenced
to pressure `<font color="#82140F"><code>.P_theta.</code></font>', is the variable assumed to exist on
the y-axis.
<p>



<!-- @node   Draw Isospice, Draw Label Boxed, Draw Isopycnal, Draw -->
<a name="DrawIsospice" ></a>
<h4>9.3.9.18: `<font color="#82140F"><code>draw isospice</code></font>'</h4>

<!-- latex: \index{draw isospice} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw isospice .spice. [unlabelled]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw an iso-spice line for a "TS" diagram, using (S, T) data stored in
files in a subdirectory named `<font color="#82140F"><code>iso-spice0</code></font>' in a directory named by
the unix environment variable `<font color="#82140F"><code>GRI_EOS_DIR</code></font>'.  You must set this
environment variable yourself, in the normal unix way.  If
`<font color="#82140F"><code>GRI_EOS_DIR</code></font>' is not defined, Gri looks in the directory
`<font color="#82140F"><samp>/data/po/ocean/EOS/iso0</samp></font>'; of course, this will work only
for people on the same machine as the author.
<p>
Only certain iso-spice lines are stored in these files, so only certain
values of `<font color="#82140F"><code>.spice.</code></font>' are allowed.  They are 21.75, 22.00, 22.25,
..., 30.75.  You must supply `<font color="#82140F"><code>.density.</code></font>' in exactly this format
(with 2 decimal places), or else Gri will not find the appropriate TS
file, and will give a "can't open file" error.  NB: isopycnals ranging
from about 23.00 to 26.00 cross a TS diagram spanning 34&lt;S&lt;36 and
0&lt;T&lt;10.
<p>
The line is labelled at the right with the density value, unless the
`<font color="#82140F"><code>unlabelled</code></font>' option is given.
<p>
Clipping should be on when drawing iso-spice lines.  A warning will be
given if the isospice line does not intersect the clipping region.
<p>
EXAMPLE
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
set clip on
draw isospice line 27.00
draw isospice line 27.50 unlabelled
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

<!-- @node   Draw Label Boxed, Draw Label Whiteunder, Draw Isospice, Draw -->
<a name="DrawLabelBoxed" ></a>
<h4>9.3.9.19: `<font color="#82140F"><code>draw label</code></font>'</h4>

<!-- latex: \index{draw label boxed} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw label boxed "string" at .xleft. .ybottom. [cm]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw boxed label for plot, located with lower-left corner at indicated
(x,y) position (specified in user units or in cm on the page).  The
current font size and pen color are used.  The geometry derives from the
current font size, with the label being centered within the box.
<p>

<!-- @node   Draw Label Whiteunder, Draw Label For Last Curve, Draw Label Boxed, Draw -->
<a name="DrawLabelWhiteunder" ></a>
<h4>9.3.9.20: `<font color="#82140F"><code>draw label whiteunder</code></font>'</h4>

<!-- latex: \index{draw label whiteunder} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw label whiteunder "\string" at .xleft. .ybottom. [cm]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw label for plot, located with lower-left corner at indicated (x,y)
position (specified in user units or in cm on the page).  Whiteout is
used to clean up the area under the label.  BUGS: Cannot handle angled
text; doesn't check for super/subscripts.
<p>

<!-- @node   Draw Label For Last Curve, Draw Label, Draw Label Whiteunder, Draw -->
<a name="DrawLabelForLastCurve" ></a>
<h4>9.3.9.21: `<font color="#82140F"><code>draw label for last curve</code></font>'</h4>

<!-- latex: \index{draw label for last curve} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw label for last curve "label"'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a label for the last curve drawn, using the `<font color="#82140F"><code>..xlast..</code></font>' and
`<font color="#82140F"><code>..ylast..</code></font>' built-in variables.
<p>

<!-- @node   Draw Label, Draw Line From, Draw Label For Last Curve, Draw -->
<a name="DrawLabel" ></a>
<h4>9.3.9.22: `<font color="#82140F"><code>draw label</code></font>'</h4>

<!-- latex: \index{draw label} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw label "\string" [centered|rightjustified] \
    at .x. .y. [cm|pt] \
    [rotated .deg.]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With no optional parameters, draw string at given location in USER units.
<p>
With the `<font color="#82140F"><code>cm</code></font>' or `<font color="#82140F"><code>pt</code></font>' keyword is present, the location is in
centimetres or points on the page.
<p>
With the `<font color="#82140F"><code>rotated</code></font>' keyword present, the angle in degrees from the
horizontal, measured positive in the counterclockwise direction, is
given.
<p>
With the keyword `<font color="#82140F"><code>centered</code></font>' present, the text is centered at the
given location; similarly the keyword `<font color="#82140F"><code>rightjustified</code></font>' makes the
text end at the given location.
<p>


<!-- @node   Draw Line From, Draw Line Legend, Draw Label, Draw -->
<a name="DrawLineFrom" ></a>
<h4>9.3.9.23: `<font color="#82140F"><code>draw line from ... to</code></font>'</h4>

<!-- latex: \index{draw line} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw line from .x0. .y0. to .x1. .y1. [cm|pt]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With no optional parameters, draw a line from (`<font color="#82140F"><code>.x0.</code></font>',
`<font color="#82140F"><code>.y0.</code></font>')  to (`<font color="#82140F"><code>.x1.</code></font>', `<font color="#82140F"><code>.y1</code></font>'.), where coordinates are in
user units.  With the `<font color="#82140F"><code>cm</code></font>' or `<font color="#82140F"><code>pt</code></font>' keyword present, the
coordinates are in centimetres or points on the page.  NOTE: This will
not cause auto-drawing of axes.
<p>


<!-- @node   Draw Line Legend, Draw Lines, Draw Line From, Draw -->
<a name="DrawLineLegend" ></a>
<h4>9.3.9.24: `<font color="#82140F"><code>draw line legend</code></font>'</h4>

<!-- latex: \index{draw line legend} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw line legend "label" at .x. .y. [cm] [length .cm.]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a legend identifying the current line type with the given label.  A
short horizontal line is drawn starting at the location (`.x.',
`<font color="#82140F"><code>.y.</code></font>'), which may be specified in centimetres or, the default, in
user coordinates.  The line length is normally 1 cm, but this length can
be set by the last option.  The indicated label string is drawn 0.25 cm
to the right of the line.
     
<b>See also</b> `<font color="#82140F"><code>draw symbol legend ...</code></font>'.
     
EXAMPLE (of keeping track of the desired location for the legend)
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
.offset. = 1                    # cm to offset legends
# ... get salinity data
set line width 0.25
draw curve
draw line legend "Salinity" at .x. .y. 
# ... get temperature data
set line width 1.0
set dash 0.45 0.05
draw curve
.y. += .offset.
draw line legend "Temperature" at .x. .y.
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

<!-- @node   Draw Lines, Draw Patches, Draw Line Legend, Draw -->
<a name="DrawLines" ></a>
<h4>9.3.9.25: `<font color="#82140F"><code>draw lines</code></font>'</h4>

<!-- latex: \index{draw lines} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw lines {vertically .left. .right. .inc.} | \
    {horizontally .bottom. .top. .inc.}'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw several lines, either vertically or horizontally.  This can be
useful in drawing gridlines for axes, etc.  The following example shows
how to draw thin gray lines extending from the labelled tics on the x
axis (ie, at 0, 0.1, 0.2, ... 1):
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
set x axis 0 1 0.1 0.05
set y axis 10 20 10
draw axes
set graylevel 0.75
set line width 0.5
draw lines vertically 0 1 0.1
set graylevel 0
</font></PRE>
</TD>
</TR>
</TABLE>
<p>



<!-- @node   Draw Patches, Draw Polygon, Draw Lines, Draw -->
<a name="DrawPatches" ></a>
<h4>9.3.9.26: `<font color="#82140F"><code>draw patches</code></font>'</h4>

<!-- latex: \index{draw patches} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw patches .width. .height. [cm]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With the optional `<font color="#82140F"><code>cm</code></font>' keyword not present, draw column data z(x,y)
as gray patches according to the grayscale as set by most recent
`<font color="#82140F"><code>set image grayscale</code></font>'.  The patches are aligned along the
horizontal, and have the indicated size in user units.
<p>
With the optional keyword `<font color="#82140F"><code>cm</code></font>' is present, the patch size is
specified in centimetres.
<p>



<!-- @node   Draw Polygon, Draw Regression Line, Draw Patches, Draw -->
<a name="DrawPolygon" ></a>
<h4>9.3.9.27: `<font color="#82140F"><code>draw polygon</code></font>'</h4>

<!-- latex: \index{draw polygon} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw polygon [filled] .x0. .y0. .x1. .y1. [other pairs] [user|cm|pt]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a polygon connecting the indicated points, specified in user
units.  The last point is joined to the first by a line segment.  At
least two points must be specified.  If the `<font color="#82140F"><code>filled</code></font>' keyword is
present, the polygon is filled with the current pen color.  If no unit
is given, user units are used.
<p>

<!-- @node   Draw Regression Line, Draw Symbol At, Draw Polygon, Draw -->
<a name="DrawRegressionLine" ></a>
<h4>9.3.9.28: `<font color="#82140F"><code>draw regression line</code></font>'</h4>

<!-- latex: \index{draw regression line} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw regression line [clipped]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Fit and draw a regression line to column data, of the form
 `<font color="#82140F"><code>y = ..coeff0.. + ..coeff1.. * x</code></font>', exporting `<font color="#82140F"><code>..coeff0..</code></font>',
`<font color="#82140F"><code>..coeff0_sig..</code></font>', `<font color="#82140F"><code>..coeff1..</code></font>'  and `<font color="#82140F"><code>..coeff1_sig..</code></font>'  as
global variables (see <a href="Regress.html#Regress">Regress</a>).
<p>

Normally, the line is not clipped to the axes frame, but it will be if
the keyword `<font color="#82140F"><code>clipped</code></font>' is given.
<p>

HINT: to label the plot you might do the following:
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
sprintf \label "y = %f + %f * x. R$^2$=%f" \
  ..coeff0.. ..coeff1.. ..R2..
draw title "The linear fit is \label"
</font></PRE>
</TD>
</TR>
</TABLE>
     
<p>

<!-- @node   Draw Symbol At, Draw Symbol Legend, Draw Regression Line, Draw -->
<a name="DrawSymbolAt" ></a>
<h4>9.3.9.29: `<font color="#82140F"><code>draw symbol ... at</code></font>'</h4>

<!-- latex: \index{draw symbol at} -->


<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw symbol .code.|\name at .x. .y. [cm|pt]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a symbol at given (single) location.  The location is normally in
user coordinates; it will be in centimetres on the page if the optional
`<font color="#82140F"><code>cm</code></font>' or `<font color="#82140F"><code>pt</code></font>' keyword is given.
<p>
With the optional numerical/name code specified, then the symbol of
that number or name is drawn at each (x,y) datum, whether or not a
z-column exists.  The numerical/name codes are:
<p>
<center><IMG SRC="./resources/symbols.gif" ALT="Symbols in gri"></center> 
<p> 



<!-- @node   Draw Symbol Legend, Draw Symbol, Draw Symbol At, Draw -->
<a name="DrawSymbolLegend" ></a>
<h4>9.3.9.30: `<font color="#82140F"><code>draw symbol legend</code></font>'</h4>

<!-- latex: \index{draw symbol legend} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw symbol legend \symbol_name "label" \
    at .x. .y. [cm]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw indicated symbol at indicated location, with the indicated label
beside it.  The label is drawn one M-space to the right of the symbol,
vertically centered on the indicated `<font color="#82140F"><code>.y.</code></font>' location.
<p>


<!-- @node   Draw Symbol, Draw Time Stamp, Draw Symbol Legend, Draw -->
<a name="DrawSymbol" ></a>
<h4>9.3.9.31: `<font color="#82140F"><code>draw symbol</code></font>'</h4>

<!-- latex: \index{draw symbol} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw symbol [[.code.|\name]    \
    | [graylevel z]             \
      [color [hue z|.h.]        \
             [brightness .b.]   \
             [saturation .s.]]]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

With no optional parameters, draw symbols at the (x,y) data.  If a
z-column has been read with `<font color="#82140F"><code>read columns</code></font>', then its value codes
the symbol to draw, according to the table below.  (The value of z is
first rounded to the nearest integer.)  If no z-column has been read,
the symbol X is drawn at each datum.
<p>
With the optional numerical/name code specified, then the symbol of
that number or name is drawn at each (x,y) datum, whether or not a
z-column exists.  The numerical/name codes are:
<center><IMG SRC="./resources/symbols.gif" ALT="Symbols in Gri"></center> 
<p> 
<p>

With the optional `<font color="#82140F"><code>graylevel z</code></font>' fields specified, the graylevel is
given by the `<font color="#82140F"><code>z</code></font>' column (0=black, 1=white).
<p>
With the optional `<font color="#82140F"><code>color</code></font>' field specified, the color is
specified, either directly in the command (the `<font color="#82140F"><code>hue .h.</code></font>' form) or
in the z column.  For more information on color, refer to the 
`<font color="#82140F"><code>set color hsb ...</code></font>' command.
<p>
Examples: both `<font color="#82140F"><code>draw symbol bullet color</code></font>' and 
`<font color="#82140F"><code>draw symbol bullet color hue z</code></font>' draw bullets whose hue is given by
the value in the z column.  The hue (or the color, in other words)
blends smoothly across the spectrum as the numerical value ranges from 0
to 1.  The value 0yields red, 1/3 yields green, 2/3 yields blue, etc.
If the `<font color="#82140F"><code>brightness</code></font>' and the `<font color="#82140F"><code>saturation</code></font>' are not specified,
they both default to the value 1, which yields pure, bright colors.
<p>
Example: draw all in green dots
`<font color="#82140F"><code>draw symbol bullet color hue 0.333 brightness 1 saturation 1</code></font>'
<p>

Example: display spectrum of dots
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
set symbol size 0.3
open "awk 'END{ \
    for(c=0;c&lt;1;c+=1/40) \
        print(c,c,c)}' | "
read columns x y z
close
draw symbol bullet color hue z
</font></PRE>
</TD>
</TR>
</TABLE>
<p>



<!-- @node   Draw Time Stamp, Draw Title, Draw Symbol, Draw -->
<a name="DrawTimeStamp" ></a>
<h4>9.3.9.32: `<font color="#82140F"><code>draw time stamp</code></font>'</h4>

<!-- latex: \index{draw times stamp} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw time stamp \
    [fontsize .points. \
        [at .x_cm. .y_cm. cm \
            [with angle .deg.]]]'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw the command-file name, PostScript file name, and time, at the top
of graph.  Normally, the timestamp is drawn at the top of the page, in a
fontsize of 10 points.  But the user can specify the fontsize, and
additionally the location (in cm) and additionally the angle measured in
degrees anticlockwise from the horizontal.
<p>
NOTE: If you want to have the plot drawn in landscape mode, ensure
that `<font color="#82140F"><code>set page landscape</code></font>' precedes `<font color="#82140F"><code>draw time stamp.</code></font>'
<p>


<!-- @node   Draw Title, Draw Values, Draw Time Stamp, Draw -->
<a name="DrawTitle" ></a>
<h4>9.3.9.33: `<font color="#82140F"><code>draw title</code></font>'</h4>

<!-- latex: \index{draw title} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
`draw title "\string"'
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw the indicated string above the plot.
<p>


<!-- @node   Draw Values, Draw X Axis, Draw Title, Draw -->
<a name="DrawValues" ></a>
<h4>9.3.9.34: `<font color="#82140F"><code>draw values</code></font>'</h4>

<!-- latex: \index{draw values} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw values                 \
    [.dx. .dy.]             \
    [\format]               \
    [separation .xcm. .ycm.]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw values of `<font color="#82140F"><code>z</code></font>' column, at corresponding (`<font color="#82140F"><code>x</code></font>', `<font color="#82140F"><code>y</code></font>')
locations.  If the `<font color="#82140F"><code>separation</code></font>' keyword is present, the distance
between successive points is checked, and points are skipped unless the
x and y separations exceed the indicated distances.
<p>
<ul>
<p>
<li> `<font color="#82140F"><code>draw values</code></font>'
Draw the values of `<font color="#82140F"><code>z(x,y)</code></font>', positioned 1/2 M-space to the right of
`<font color="#82140F"><code>(x,y)</code></font>' and vertically centred on `<font color="#82140F"><code>y</code></font>'.  The values are written
in a good general format known as `<font color="#82140F"><code>%lg</code></font>', in C terminology.
<p>
<li> `<font color="#82140F"><code>draw values %.2f</code></font>'
Draw values of `<font color="#82140F"><code>z(x,y)</code></font>' positioned as described above, but using
the indicated format string.  This format string specifies that 2
numbers be used after the decimal place, and that floating point should
be used.  See any C manual for format codes.
<p>
<li> `<font color="#82140F"><code>draw values .dx. .dy.</code></font>'
Print values of `<font color="#82140F"><code>z(x,y)</code></font>' at indicated offset vector
(`<font color="#82140F"><code>.dx.</code></font>',`<font color="#82140F"><code>.dy.</code></font>'), measured in centimeters, from the values of
`<font color="#82140F"><code>(x,y)</code></font>' at which the data are defined.
<p>
<li> `<font color="#82140F"><code>draw values .dx. .dy. %.3f</code></font>'
Print values of `<font color="#82140F"><code>z(x,y)</code></font>' at indicated distance from `<font color="#82140F"><code>(x,y)</code></font>',
indicated format.
</ul>
<p>


<!-- @node   Draw X Axis, Draw X Box Plot, Draw Values, Draw -->
<a name="DrawXAxis" ></a>
<h4>9.3.9.35: `<font color="#82140F"><code>draw x axis</code></font>'</h4>

<!-- latex: \index{draw x axis} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw x axis [at bottom|top|{.y. [cm]} [lower|upper]]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw an x axis, optionally at a specified location and of a specified
style.
<ul>
<p>
<li> `<font color="#82140F"><code>draw x axis</code></font>'
Draw a lower x axis (ie, one with the numbers below the line) at the
bottom of the box defined by `<font color="#82140F"><code>set y axis</code></font>'.
<p>
<li> `<font color="#82140F"><code>draw x axis at bottom</code></font>'
Draw a lower x axis (ie, one with the numbers below the line) at the
bottom of the box defined by `<font color="#82140F"><code>set y axis</code></font>'.
<p>
<li> `<font color="#82140F"><code>draw x axis at top</code></font>'
Draw an upper x axis (ie, one with the numbers above the line) at the
top of the box defined by `<font color="#82140F"><code>set y axis</code></font>' (or above any existing
stacked x axes there)
<p>
<li> `<font color="#82140F"><code>draw x axis at .y.</code></font>'
Draw a lower x axis at indicated value of `<font color="#82140F"><code>.y.</code></font>'.
<p>
<li> `<font color="#82140F"><code>draw x axis at .y. upper</code></font>'
Draw an upper x axis at indicated value of .y.
</ul>
<p>


<!-- @node   Draw X Box Plot, Draw Y Axis, Draw X Axis, Draw -->
<a name="DrawXBoxPlot" ></a>
<h4>9.3.9.36: `<font color="#82140F"><code>draw x box plot</code></font>'</h4>

<!-- latex: \index{draw x box plot} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw x box plot at .y. [size .cm.]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw Tukey box plots (which give a summary of histogram properties).
Box plots were invented by Tukey for eda (exploratory data analysis).
The centre of the box is the median.  The box edges show the first
quartile (q1) and the third quartile (q3).  The distance from q3 to q1
is called the inter-quartile range.  The whiskers (i.e., the lines with
crosses at the end) extend from q1 and q3 to the furthest data points
which are still within a distance of 1.5 inter-quartile ranges from q1
and q3.  Beyond the whiskers, all outliers are shown: open circles are
used for data within a distance of 3 inter-quartile ranges beyond q1 and
q3, and in closed circles beyond that.
<p>
As a side effect, this command stores q1, q2, and q3 
into variables `<font color="#82140F"><code>..q1..</code></font>', `<font color="#82140F"><code>..q2..</code></font>', and `<font color="#82140F"><code>..q3..</code></font>'.
<p>

<ul>
<p>
<li> `<font color="#82140F"><code>draw x box plot at .y.</code></font>'
Draw Tukey's box plot, spreading in the x direction, centered at
y=`<font color="#82140F"><code>.y.</code></font>' and of default width 0.5 cm.
<p>
<li> `<font color="#82140F"><code>draw x box plot at .y. size .cm.</code></font>'
Draw Tukey's box plot, spreading in the x direction, centered at
y=`<font color="#82140F"><code>.y.</code></font>' and of width `<font color="#82140F"><code>.cm.</code></font>' centimetres.
</ul>
<p>


<!-- @node   Draw Y Axis, Draw Y Box Plot, Draw X Box Plot, Draw -->
<a name="DrawYAxis" ></a>
<h4>9.3.9.37: `<font color="#82140F"><code>draw y axis</code></font>'</h4>

<!-- latex: \index{draw y axis} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw y axis [at left|right|{.x. cm} [left|right]]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw a y axis, optionally at a specified location and of a specified
style.
<p>
<ul>
<p>
<li> `<font color="#82140F"><code>draw y axis</code></font>'
Draw a left-hand-side y axis (ie, one with the numbers to the left of
the line) at left of box defined by `set x axis'
<p>
<li> `<font color="#82140F"><code>draw y axis at left</code></font>'
Draw a left-hand-side y axis (ie, one with the numbers to the left of
the line) at left of box defined by `<font color="#82140F"><code>set x axis</code></font>'.
<p>
<li> `<font color="#82140F"><code>draw y axis at right</code></font>'
Draw a right-hand-side y axis (ie, one with the numbers to the right of
the line) at right of box defined by `<font color="#82140F"><code>set x axis</code></font>'.
<p>
<li> `<font color="#82140F"><code>draw y axis at .x.</code></font>'
Draw a left-hand-side y axis (ie, one with the numbers to the left of
the line) at indicated value of `<font color="#82140F"><code>.x.</code></font>'
<p>
<li> `<font color="#82140F"><code>draw y axis at .x. right</code></font>'
Draw a right-hand-side y axis (ie, one with the numbers to the right of
the line) at indicated value of `<font color="#82140F"><code>.x.</code></font>'
</ul>
<p>


<!-- @node   Draw Y Box Plot, Draw Zero Line, Draw Y Axis, Draw -->
<a name="DrawYBoxPlot" ></a>
<h4>9.3.9.38: `<font color="#82140F"><code>draw y box plot</code></font>'</h4>

<!-- latex: \index{draw y box plot} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw y box plot at .x. [size .cm]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw Tukey box plots (which give summary of histogram properties).
<ul>
<p>
<li> `<font color="#82140F"><code>draw y box plot at .x.</code></font>'
Draw Tukey's box plot, spreading in the y direction, centered at
x=`<font color="#82140F"><code>.x.</code></font>' and of default width 0.5 cm.
<p>
<li> `<font color="#82140F"><code>draw y box plot at .x. size .cm.</code></font>'
Draw Tukey's box plot, spreading in the y direction, centered at
x=`<font color="#82140F"><code>.x.</code></font>' and of width `<font color="#82140F"><code>.cm.</code></font>' centimetres.
</ul>
<p>
As a side effect, this command stores q1, q2, and q3 
into variables `<font color="#82140F"><code>..q1..</code></font>', `<font color="#82140F"><code>..q2..</code></font>', and `<font color="#82140F"><code>..q3..</code></font>'.
<p>


<!-- @node   Draw Zero Line, End Group, Draw Y Box Plot, Draw -->
<a name="DrawZeroLine" ></a>
<h4>9.3.9.39: `<font color="#82140F"><code>draw zero line</code></font>'</h4>

<!-- latex: \index{draw zero line} -->

<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
draw zero line [horizontally|vertically]
</font></PRE>
</TD>
</TR>
</TABLE>
<p>

Draw lines corresponding to x=0 or y=0.
<ul>
<p>
<li> `<font color="#82140F"><code>draw zero line</code></font>'
Draw line y=0 if it is within axes.
<p>
<li> `<font color="#82140F"><code>draw zero line horizontally</code></font>'
Draw line y=0 if it is within axes.
<p>
<li> `<font color="#82140F"><code>draw zero line vertically</code></font>'
Draw line x=0 if it is within axes.
</ul>
<p>

</table>
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