/usr/share/doc/libplplot11/examples/f95/x22f.f90 is in libplplot-dev 5.9.9-2ubuntu2.
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! Vector plot demo.
!
! Copyright (C) 2004 Alan W. Irwin
! Copyright (C) 2004 Andrew Ross
!
! 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
! Does several contour plots using different coordinate mappings.
use plplot
implicit none
integer narr
logical fill
parameter (narr=6)
real(kind=plflt) arrow_x(narr),arrow_y(narr), &
arrow2_x(narr),arrow2_y(narr)
data arrow_x/-0.5_plflt, 0.5_plflt, 0.3_plflt, 0.5_plflt, 0.3_plflt, 0.5_plflt/
data arrow_y/0._plflt, 0._plflt, 0.2_plflt, 0._plflt, -0.2_plflt, 0._plflt/
data arrow2_x/-0.5_plflt, 0.3_plflt, 0.3_plflt, 0.5_plflt, 0.3_plflt, 0.3_plflt/
data arrow2_y/0._plflt, 0._plflt, 0.2_plflt, 0._plflt, -0.2_plflt, 0._plflt/
! Process command-line arguments
call plparseopts(PL_PARSE_FULL)
call plinit
call circulation
fill = .false.
! Set arrow style using arrow_x and arrow_y the
! plot using these arrows
call plsvect(arrow_x, arrow_y, fill)
call constriction
! Set arrow style using arrow_x and arrow_y the
! plot using these arrows
fill = .true.
call plsvect(arrow2_x, arrow2_y, fill)
call constriction
call potential
call plend
end
! vector plot of the circulation around the origin
subroutine circulation()
use plplot
implicit none
integer i, j, nx, ny
parameter (nx=20, ny=20)
real(kind=plflt) u(nx, ny), v(nx, ny), xg(nx,ny), yg(nx,ny)
real(kind=plflt) dx, dy, xmin, xmax, ymin, ymax
real(kind=plflt) xx, yy, scaling
dx = 1.0_plflt
dy = 1.0_plflt
xmin = -dble(nx)/2.0_plflt*dx
xmax = dble(nx)/2.0_plflt*dx
ymin = -dble(ny)/2.0_plflt*dy
ymax = dble(ny)/2.0_plflt*dy
do i=1,nx
xx = (dble(i)-nx/2.0_plflt-0.5_plflt)*dx
do j=1,ny
yy = (dble(j)-ny/2.0_plflt-0.5_plflt)*dy
xg(i,j) = xx
yg(i,j) = yy
u(i,j) = yy
v(i,j) = -xx
enddo
enddo
call plenv(xmin, xmax, ymin, ymax, 0, 0)
call pllab('(x)', '(y)', &
'#frPLplot Example 22 - circulation')
call plcol0(2)
scaling = 0.0_plflt
call plvect(u,v,scaling,xg,yg)
call plcol0(1)
end
! vector plot of the flow through a constricted pipe
subroutine constriction()
use plplot, PI => PL_PI
implicit none
integer i, j, nx, ny
parameter (nx=20, ny=20)
real(kind=plflt) u(nx, ny), v(nx, ny), xg(nx,ny), yg(nx,ny)
real(kind=plflt) dx, dy, xmin, xmax, ymin, ymax
real(kind=plflt) xx, yy, Q, b, dbdx, scaling
dx = 1.0_plflt
dy = 1.0_plflt
xmin = -dble(nx)/2.0_plflt*dx
xmax = dble(nx)/2.0_plflt*dx
ymin = -dble(ny)/2.0_plflt*dy
ymax = dble(ny)/2.0_plflt*dy
Q = 2.0_plflt
do i=1,nx
xx = (dble(i)-dble(nx)/2.0_plflt-0.5_plflt)*dx
do j=1,ny
yy = (dble(j)-dble(ny)/2.0_plflt-0.5_plflt)*dy
xg(i,j) = xx
yg(i,j) = yy
b = ymax/4.0_plflt*(3.0_plflt-cos(PI*xx/xmax))
if (abs(yy).lt.b) then
dbdx = ymax/4.0_plflt*sin(PI*xx/xmax)*yy/b
u(i,j) = Q*ymax/b
v(i,j) = u(i,j)*dbdx
else
u(i,j) = 0.0_plflt
v(i,j) = 0.0_plflt
endif
enddo
enddo
call plenv(xmin, xmax, ymin, ymax, 0, 0)
call pllab('(x)', '(y)', &
'#frPLplot Example 22 - constriction')
call plcol0(2)
scaling = -0.5_plflt
call plvect(u,v,scaling,xg,yg)
call plcol0(1)
end
subroutine potential()
use plplot, PI => PL_PI
implicit none
integer i, j, nr, ntheta, nper, nlevel
parameter (nr=20, ntheta=20, nper=100, nlevel=10)
real(kind=plflt) u(nr, ntheta), v(nr, ntheta), z(nr, ntheta)
real(kind=plflt) xg(nr,ntheta), yg(nr,ntheta)
real(kind=plflt) clevel(nlevel), px(nper), py(nper)
real(kind=plflt) xmin, xmax, ymin, ymax, zmin, zmax, rmax
real(kind=plflt) xx, yy, r, theta, scaling, dz
real(kind=plflt) eps, q1, d1, q1i, d1i, q2, d2, q2i, d2i
real(kind=plflt) div1, div1i, div2, div2i
rmax = dble(nr)
eps = 2.0_plflt
q1 = 1.0_plflt
d1 = rmax/4.0_plflt
q1i = - q1*rmax/d1
d1i = rmax**2.0_plflt/d1
q2 = -1.0_plflt
d2 = rmax/4.0_plflt
q2i = - q2*rmax/d2
d2i = rmax**2.0_plflt/d2
do i = 1, nr
r = 0.5 + dble(i-1)
do j = 1, ntheta
theta = 2.*PI/dble(ntheta-1)*(dble(j)-0.5)
xx = r*cos(theta)
yy = r*sin(theta)
xg(i,j) = xx
yg(i,j) = yy
div1 = sqrt((xg(i,j)-d1)**2 + (yg(i,j)-d1)**2 + eps**2)
div1i = sqrt((xg(i,j)-d1i)**2 + (yg(i,j)-d1i)**2 + eps**2)
div2 = sqrt((xg(i,j)-d2)**2 + (yg(i,j)+d2)**2 + eps**2)
div2i = sqrt((xg(i,j)-d2i)**2 + (yg(i,j)+d2i)**2 + eps**2)
z(i,j) = q1/div1 + q1i/div1i + q2/div2 + q2i/div2i
u(i,j) = -q1*(xx-d1)/div1**3 - q1i*(xx-d1i)/div1i**3 - &
q2*(xx-d2)/div2**3 - q2i*(xx-d2i)/div2i**3
v(i,j) = -q1*(yy-d1)/div1**3 - q1i*(yy-d1i)/div1i**3 - &
q2*(yy+d2)/div2**3 - q2i*(yy+d2i)/div2i**3
enddo
enddo
call a2mnmx(xg, nr, ntheta, xmin, xmax, nr)
call a2mnmx(yg, nr, ntheta, ymin, ymax, nr)
call a2mnmx(z, nr, ntheta, zmin, zmax, nr)
call plenv(xmin, xmax, ymin, ymax, 0, 0)
call pllab('(x)', '(y)', &
'#frPLplot Example 22 - potential gradient vector plot')
! plot contours of the potential
dz = abs(zmax - zmin)/dble (nlevel)
do i = 1, nlevel
clevel(i) = zmin + (i-0.5_plflt)*dz
enddo
call plcol0(3)
call pllsty(2)
call plcont(z,1,nr,1,ntheta,clevel,xg,yg)
call pllsty(1)
call plcol0(1)
call plcol0(2)
scaling = 25.0_plflt
call plvect(u,v,scaling,xg,yg)
call plcol0(1)
do i=1,nper
theta = 2.0_plflt*PI/dble(nper-1)*dble(i)
px(i) = rmax*cos(theta)
py(i) = rmax*sin(theta)
enddo
call plline(px,py)
end
!----------------------------------------------------------------------------
! Subroutine a2mnmx
! Minimum and the maximum elements of a 2-d array.
subroutine a2mnmx(f, nx, ny, fmin, fmax, xdim)
use plplot
implicit none
integer i, j, nx, ny, xdim
real(kind=plflt) f(xdim, ny), fmin, fmax
fmax = f(1, 1)
fmin = fmax
do j = 1, ny
do i = 1, nx
fmax = max(fmax, f(i, j))
fmin = min(fmin, f(i, j))
enddo
enddo
end
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