Draw a line in a pm3d map

Question

I have a and I want to overplot on it a .

Answer 1

If you set pm3d, this style is used for all plots unless you explicitely specify a different plotting style. So you must use

splot "file.txt" u (fact1)*(($1)**(-1.5)):(fact2)*(($2)**(-1.5)):6 ,\
      "line.txt" with lines 

in order to plot line.txt as line: