In my simulations, I have two numerical grids that overlap each other. One of them (the smaller one) is not rectangular but has a curved boundary (at least the area in which I care about it).
I would like to visualize those two numerical grids and how they overlap each other in gnuplot as a 2D plot. The result should look similar to this:
The red grid spans the entire area, the black grid is a subset of the red one with a curved boundary. The blue line is an approximation of the boundary.
This looks good so far, except for the fact that this is a 3D-plot at which I look exactly from above; i.e. in gnuplot I can rotate it if I wanted to.
gnuplot> show view
view is 0 rot_x, 270 rot_z, 1 scale, 1 scale_z
Viewed from this angle none of the information of the z-axis is visible. It sort of removes the reason for a 3D plot as all you can see are the grids on which your data live. And this is precisely what I want.
But then, I rather have a 2D plot since those are more efficient to handle in gnuplot and also gnuplot generates a huge margin around 3D plots which reduces the useable area. How can I get this mesh projected into a 2D plane and get gnuplot to visualise it?
How to create above plot: I have one variable that is defined on the entire grid, but is non-zero (and always positive) only on the black part of the grid. The data are stored in the file "values.dat" in the usual way---in three columns in polar coordinates:
r (radius) -- theta (polar angle) -- value
Then you can get above plot with:
set style line 1 lt 1 dt 3 lc rgb "red"
set style line 2 lt 1 lc rgb "black"
set view 0, 270, 1, 1
splot "values.dat" u 1:2:(1.0) w l ls 1, \
"values.dat" u 1:2:($3>0.0?1.0:NaN) w l ls 2
The blue line in the graph is additional and comes from a separate approximation of the grid boundary but is not really relevant for the question here.
set view mapcommand in gnuplot did exactly what I want! Success! – Christian K