Octave mapping

I studied physical chemistry, met some of the formula equation of state, I thought I could make a diagram of a verification verification on the computer. . .

% Set values and precision mapping section ↓ 
X = Y = linspace (0.01,0.2,100); 
[XX, YY] = meshgrid now (X, Y); 
% write your equations ↓ 
ZZ = ./. 1 (. * XX YY); 
% plotted ↓ 
Surf (XX, YY, ZZ);

 

FIG Ideal Gas: