## 3. Contours, Raster Maps and Surfaces

This section illustrates the use of plotmtv in viewing data sets of the form z = f(x,y)
where x and y range over a rectangular mesh. The following code, cont.f illustrates the
construction of an MTV data file containing the information necessary to plot the function
over the region 0 < x,y < 5.

program cont
parameter(mmax=25,nmax=25)
parameter(xmin=0.0,ymin=0.0,xmax=5.0,ymax=5.0)
parameter(dx=(xmax-xmin)/mmax,dy=(ymax-ymin)/nmax)
dimension u(0:mmax,0:nmax)
write(6,*)'Available contour styles are:'
write(6,*)'normal contours -- contstyle = 1'
write(6,*)'gradated colors -- contstyle = 2'
write(6,*)'3D surface mesh -- contstyle = 3'
write(6,*)'Please enter a value for contstyle'
read*,i
open(4,file='test1.dat',status='unknown')
c Specify that data are to be contoured
write(4,*)'$DATA=CONTOUR'
c Specify the style of the contour map
write(4,*)'%contstyle=',i
c Set the number of data points in the x and y directions
write(4,*)'%nx=',mmax+1
write(4,*)'%ny=',nmax+1
c Set the maximum and minimum x and y-values
write(4,*)'%xmin=',xmin
write(4,*)'%ymin=',ymin
write(4,*)'%xmax=',xmax
write(4,*)'%ymax=',ymax
c Set the number of contours to display
write(6,*)' '
write(6,*)'Enter the number of contours to display'
read*,nsteps
write(4,*)'%nsteps=',nsteps
y = ymin
do 1 n = 0,nmax
x = xmin
do 2 m = 0,mmax
u(m,n) = x*x - y*y
x = x + dx
2 continue
y = y + dy
1 continue
do 3 n = 0,nmax
write(4,100)(u(m,n),m=0,mmax)
3 continue
100 format(100f10.2)
close(4)
end

Compile and run Code 2, then experiment with different choices of values for
contstyle and number of contours.
Click here to have plotmtv
plot contours.

Figure 2 shows a traditional contour map of the function .
It was created
using the command line options -pfg BLACK -pbg GRAY. Use the 2D/3D toggle, (left
click in the box 2D Plot or 3D Plot) to view a stacked contour map of this function. It does
not appear to be possible to change the color of contour lines using the present version of plotmtv.

Figure 2 Plot from Code 2 with contstyle=1 and nsteps=20

Figure 3 shows a 2D raster map representation of the function
. It was
created using the command line options -pfg BLACK -pbg WHITE. Again, use the 2D/3D
toggle to view a colored surface map of the function. In 3D display mode both the height
of the surface and the color of the surface represent the value of the function at a given
point. While in 3D mode, left click on the boxes labeled Left, Right, Up and Down to
obtain different views of the data set.

Figure 3 Plot from Code 2 using contstyle=2 and nsteps=20

Figure 4 provides a wire frame surface plot of the function . As with
Figure 3, the plot can be rotated and tilted to obtain different viewpoints. Use the toggle
Wire Frame/Hidden Lines to switch between a wire frame display and an opaque surface
display.

Figure 4 Plot from Code 2 with contstyle=3 and nsteps=20