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Sample plots using date / time formatting for axes
Copyright (C) 2007 Andrew Ross
Copyright (C) 2008 Hezekiah M. Carty
This file is part of PLplot.
PLplot is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published
by the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
PLplot is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with PLplot; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*)
open Plplot
open Printf
let pi = atan 1.0 *. 4.0
(* Plot a model diurnal cycle of temperature *)
let plot1 () =
(* Data points every 10 minutes for 1 day *)
let npts = 73 in
let xmin = 0.0 in
let xmax = 60.0 *. 60.0 *. 24.0 in (* Number of seconds in a day *)
let ymin = 10.0 in
let ymax = 20.0 in
let x =
Array.init npts (fun i -> xmax *. float_of_int i /. float_of_int npts)
in
let y =
Array.init npts (
fun i ->
15.0 -. 5.0 *. cos (2.0 *. pi *. (float_of_int i /. float_of_int npts))
)
in
(* Set x error bars to +/- 5 minute *)
let xerr1 = Array.map (fun xi -> xi -. 60.0 *. 5.0) x in
let xerr2 = Array.map (fun xi -> xi +. 60.0 *. 5.0) x in
(* Set y error bars to +/- 0.1 deg C *)
let yerr1 = Array.map (fun yi -> yi -. 0.1) y in
let yerr2 = Array.map (fun yi -> yi +. 0.1) y in
pladv 0;
(* Rescale major ticks marks by 0.5 *)
plsmaj 0.0 0.5;
(* Rescale minor ticks and error bar marks by 0.5 *)
plsmin 0.0 0.5;
plvsta ();
plwind xmin xmax ymin ymax;
(* Draw a box with ticks spaced every 3 hour in X and 1 degree C in Y. *)
plcol0 1;
(* Set time format to be hours:minutes *)
pltimefmt "%H:%M";
plbox "bcnstd" (3.0 *. 60.0 *. 60.0) 3 "bcnstv" 1.0 5;
plcol0 3;
pllab "Time (hours:mins)" "Temperature (degC)" "#frPLplot Example 29 - Daily temperature";
plcol0 4;
plline x y;
plcol0 2;
plerrx xerr1 xerr2 y;
plcol0 3;
plerry x yerr1 yerr2;
(* Rescale major / minor tick marks back to default *)
plsmin 0.0 1.0;
plsmaj 0.0 1.0;
()
(* Plot the number of hours of daylight as a function of day for a year *)
let plot2 () =
(* Latitude for London *)
let lat = 51.5 in
let npts = 365 in
let xmin = 0.0 in
let xmax = float_of_int npts *. 60.0 *. 60.0 *. 24.0 in
let ymin = 0.0 in
let ymax = 24.0 in
let x = Array.make npts 0.0 in
let y = Array.make npts 0.0 in
(* Formula for hours of daylight from
* "A Model Comparison for Daylength as a Function of Latitude and
* Day of the Year", 1995, Ecological Modelling, 80, pp 87-95. *)
for j = 0 to npts - 1 do
x.(j) <- float_of_int j *. 60.0 *. 60.0 *. 24.0;
let p =
asin (0.39795 *. cos (0.2163108 +. 2.0 *.
atan (0.9671396 *. tan (0.00860 *. (float_of_int j -. 186.0))))
)
in
let d =
24.0 -. (24.0 /. pi) *. acos (( sin (0.8333 *. pi /. 180.0) +.
sin (lat *. pi /. 180.0) *. sin p) /.
(cos (lat *. pi /. 180.0) *. cos p)
)
in
y.(j) <- d;
done;
plcol0 1;
(* Set time format to be abbreviated month name followed by day of month *)
pltimefmt "%b %d";
plprec 1 1;
plenv xmin xmax ymin ymax 0 40;
plcol0 3;
pllab "Date" "Hours of daylight" "#frPLplot Example 29 - Hours of daylight at 51.5N";
plcol0 4;
plline x y;
plprec 0 0;
()
let plot3 () =
(* Calculate seconds since the Unix epoch for 2005-12-01 UTC. *)
(* Adopt the known result for POSIX-compliant systems. *)
let tstart = 1133395200.0 in
let npts = 62 in
let xmin = tstart in
let xmax = xmin +. float_of_int npts *. 60.0 *. 60.0 *. 24.0 in
let ymin = 0.0 in
let ymax = 5.0 in
let x =
Array.init npts (fun i -> xmin +. float_of_int i *. 60.0 *. 60.0 *. 24.0)
in
let y =
Array.init npts (
fun i ->
1.0 +. sin (2.0 *. pi *. float_of_int i /. 7.0) +.
exp (float_of_int (min i (npts - i)) /. 31.0)
)
in
pladv 0;
plvsta ();
plwind xmin xmax ymin ymax;
plcol0 1;
(* Set time format to be ISO 8601 standard YYYY-MM-DD. Note that this is
equivalent to %f for C99 compliant implementations of strftime. *)
pltimefmt "%Y-%m-%d";
(* Draw a box with ticks spaced every 14 days in X and 1 hour in Y. *)
plbox "bcnstd" (14.0 *. 24.0 *. 60.0 *. 60.0) 14 "bcnstv" 1.0 4;
plcol0 3;
pllab "Date" "Hours of television watched" "#frPLplot Example 29 - Hours of television watched in Dec 2005 / Jan 2006";
plcol0 4;
(* Rescale symbol size (used by plpoin) by 0.5 *)
plssym 0.0 0.5;
plpoin x y 2;
plline x y;
()
let plot4 () =
(* TAI-UTC (seconds) as a function of time.
Use Besselian epochs as the continuous time interval just to prove
this does not introduce any issues. *)
(* Use the definition given in http://en.wikipedia.org/wiki/Besselian_epoch
* B = 1900. + (JD -2415020.31352)/365.242198781
* ==> (as calculated with aid of "bc -l" command)
* B = (MJD + 678940.364163900)/365.242198781
* ==>
* MJD = B*365.24219878 - 678940.364163900 *)
let scale = 365.242198781 in
let offset1 = -678940.0 in
let offset2 = -0.3641639 in
plconfigtime scale offset1 offset2 0x0 false 0 0 0 0 0 0.0;
let xmin = ref 0.0 in
let xmax = ref 0.0 in
let npts = ref 0 in
let ymin = ref 0.0 in
let ymax = ref 0.0 in
let time_format = ref "" in
let if_TAI_time_format = ref false in
let title_suffix = ref "" in
let xtitle = ref "" in
let xlabel_step = ref 0.0 in
for kind = 0 to 6 do
let () =
match kind with
| 0 ->
xmin := plctime 1950 0 2 0 0 0.0;
xmax := plctime 2020 0 2 0 0 0.0;
npts := 70 * 12 + 1;
ymin := 0.0;
ymax := 36.0;
time_format := "%Y%";
if_TAI_time_format := true;
title_suffix := "from 1950 to 2020";
xtitle := "Year";
xlabel_step := 10.0;
| 1
| 2 ->
xmin := plctime 1961 7 1 0 0 (1.64757 -. 0.20);
xmax := plctime 1961 7 1 0 0 (1.64757 +. 0.20);
npts := 1001;
ymin := 1.625;
ymax := 1.725;
time_format := "%S%2%";
title_suffix := "near 1961-08-01 (TAI)";
xlabel_step := 0.05 /. (scale *. 86400.0);
if kind = 1 then (
if_TAI_time_format := true;
xtitle := "Seconds (TAI)";
)
else (
if_TAI_time_format := false;
xtitle := "Seconds (TAI) labelled with corresponding UTC";
)
| 3
| 4 ->
xmin := plctime 1963 10 1 0 0 (2.6972788 -. 0.20);
xmax := plctime 1963 10 1 0 0 (2.6972788 +. 0.20);
npts := 1001;
ymin := 2.55;
ymax := 2.75;
time_format := "%S%2%";
title_suffix := "near 1963-11-01 (TAI)";
xlabel_step := 0.05 /. (scale *. 86400.0);
if kind = 3 then (
if_TAI_time_format := true;
xtitle := "Seconds (TAI)";
)
else (
if_TAI_time_format := false;
xtitle := "Seconds (TAI) labelled with corresponding UTC";
)
| 5
| 6 ->
xmin := plctime 2009 0 1 0 0 (34.0 -. 5.0);
xmax := plctime 2009 0 1 0 0 (34.0 +. 5.0);
npts := 1001;
ymin := 32.5;
ymax := 34.5;
time_format := "%S%2%";
title_suffix := "near 2009-01-01 (TAI)";
xlabel_step := 1.0 /. (scale *. 86400.0);
if kind = 5 then (
if_TAI_time_format := true;
xtitle := "Seconds (TAI)";
)
else (
if_TAI_time_format := false;
xtitle := "Seconds (TAI) labelled with corresponding UTC";
)
| _ -> failwith "Bad plot kind"
in
let x = Array.make 1001 0.0 in
let y = Array.make 1001 0.0 in
for i = 0 to !npts - 1 do
x.(i) <-
!xmin +. float_of_int i *. (!xmax -. !xmin) /. (float_of_int (!npts - 1));
plconfigtime scale offset1 offset2 0x0 false 0 0 0 0 0 0.0;
let tai = x.(i) in
(* The "full" calls to plbtime are commented out to avoid OCaml
compilation warnings. *)
(*
let tai_year, tai_month, tai_day, tai_hour, tai_min, tai_sec =
plbtime tai
in
*)
ignore (plbtime tai);
plconfigtime scale offset1 offset2 0x2 false 0 0 0 0 0 0.0;
let utc_year, utc_month, utc_day, utc_hour, utc_min, utc_sec =
plbtime tai
in
plconfigtime scale offset1 offset2 0x0 false 0 0 0 0 0 0.0;
let utc = plctime utc_year utc_month utc_day utc_hour utc_min utc_sec in
y.(i) <- (tai -. utc) *. scale *. 86400.0;
done;
pladv 0;
plvsta ();
plwind !xmin !xmax !ymin !ymax;
plcol0 1;
plconfigtime scale offset1 offset2
(if !if_TAI_time_format then 0x0 else 0x2)
false 0 0 0 0 0 0.0;
pltimefmt !time_format;
plbox "bcnstd" !xlabel_step 0 "bcnstv" 0.0 0;
plcol0 3;
let title = sprintf "#frPLplot Example 29 - TAI-UTC %s" !title_suffix in
pllab !xtitle "TAI-UTC (sec)" title;
plcol0 4;
plline (Array.sub x 0 !npts) (Array.sub y 0 !npts);
done;
()
(*--------------------------------------------------------------------------*\
* Draws several plots which demonstrate the use of date / time formats for
* the axis labels.
* Time formatting is done using the system strftime routine. See the
* documentation of this for full details of the available formats.
*
* 1) Plotting temperature over a day (using hours / minutes)
* 2) Plotting
*
* Note: Times are stored as seconds since the epoch (usually 1st Jan 1970).
\*--------------------------------------------------------------------------*)
let () =
(* Parse command line arguments *)
plparseopts Sys.argv [PL_PARSE_FULL];
(* Initialize plplot *)
plinit ();
plot1 ();
plot2 ();
plot3 ();
plot4 ();
(* Don't forget to call plend() to finish off! *)
plend();
()
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