I am trying to use inpolygon but from reading the documentation I cannot figure out how to obtain the first two inputs.

I have an 960x960 array of values called "data";
I have my polygon in X,Y

% plot image
imagesc(data); 
[X,Y] = ginput;
Now, I would like to be able to select a polygon, then find the sum of the corresponding polygon in data.

inpolygon's first two inputs are X and Y, but I do not understand how to get these from data.

Thanks