@mikrom:
IMHO: What you posted could not work.
1)
In one loop you are using step_x:
do x = x_min, x_max, step_x
...
but in the other loop you are using stepx:
do ind_x = x_min, x_max, stepx
The first code was my guess, I think this how the program I had used gave me only non-zero data. This...