Combining contours and images
Sometimes we would like to plot two related but different sets of data on the same graph. In the case of 2D plots, it's simple: we just plot any number of curves and identify them with labels or a legend. But with 3D plots, trying to interpret a graph containing two different surfaces or sets of contours would be difficult, and plotting two heat maps simultaneously would not make any sense.
The previous figure shows one way to do this: plot contours and an image map together.
How to do it…
Feed this code to gnuplot to get the previous figure:
set xrange [0:pi]
set yrange [0:pi]
set iso 100
set samp 100
set cntrparam levels 10
unset key
unset surface
set view map
set contour base
set pm3d at b
splot '++' using 1:2:($1**2-$2**2):(sin($1**2+$2**2))\
with lines lw 2How it works…
We set everything up as in the previous contour plot example, but we also put in a set pm3d at base, so we are asking for both a contour plot and a colored surface plot. How do we make...
