Plotting function in two variables only for specified domain

I would like to plot a function in two variables, so y = f(x1,x2) only a specified domain, for example for the domain {(x1,x2) : x1+x2 < 1}, but it could be every possible domain for which one can write a boolean function to check whether (x1,x2) is in the domain. How does this work?

Answer 1

[Star Strider]

Logical matrices can result in vector results that can be difficult to work with for surf, mesh, and similar plots that require matrix arguments rather than vectors. The easiest way to avoid these problems is to set the matrix elements that do not meet the set requirements to NaN, since NaN values do not plot.

Try this simple example:

[X1,X2] = meshgrid(-5:0.5:5);
LM = (X1 + X2) < 1;
X1(~LM) = NaN;
X2(~LM) = NaN;
Y = X1.^2 + X2.^3;

figure
mesh(X1, X2, Y)
grid on
view(60, 30)

Experiment with it with your own functions.

[Jan Schäppi]

Perfect, thank you very much.

[Star Strider]

As always, my pleasure.