Plotting a function inside a polygon in Matlab

I want to know if there are any ways to plot a given function with domain restricted to a polygon with given vertices, in Matlab. For example, how can i plot the function f =@(x,y) x.*y inside the polygon whose vertices are given by p1 = [0 0], p2 = [1 0], p3 = [2 2], p4 = [0 1]? I know there exists the function inpolygon but I have no idea on how to use it to plot a function only inside the polygon. Thanks in advance.

You can generate a mesh for x-y points in the bounding box of your polygon, then make points outside the polygon equal to NaN using inpolygon, then calculate the surface based on all points, which will be NaN for points outside the polygon.

From your example:

% Input function and polygon for example
f =@(x,y) x.*y;
% Polygon is [x, y] points
p = [0 0
     1 0
     2 2
     0 1];

% Generate x-y mesh for bounding box of polygon
n = 1000; % number of points in each direction
x = linspace( min(p(:,1)), max(p(:,1)), n ); % grid points for x
y = linspace( min(p(:,2)), max(p(:,2)), n ); % grid points for y
[x,y] = meshgrid( x, y ); % all x-y combinations for grid

b = inpolygon( x, y, p(:,1), p(:,2) ); % check which points are in the polygon
x(~b) = NaN; % make points outside the polygon equal to NaN
y(~b) = NaN; %   so that f(x,y) is also NaN

% Plot the patch of the original polygon and the surface f(x,y)
figure(1); clf; hold on; grid on;
patch( p(:,1), p(:,2), 'k', 'displayname', 'x-y poly' );
surf( x, y, f(x,y), 'displayname', 'f(x,y) in poly', 'edgecolor', 'flat' );
legend( 'show', 'location', 'north' ); view( 6, 25 ); colormap( 'jet' );

Example output: