using maltab to plot a matrix

Question

I have a matrix. The entries are all integers. For example, my matrix would look like this

M = 1 1 1 2 2 2 2 3 3
    1 1 1 2 2 2 2 3 0
    4 4 4 5 5 5 5 0 0
    4 4 4 5 5 5 0 0 0
    4 4 4 5 5 0 0 0 0
    4 4 4 5 0 0 0 0 0
    6 6 6 0 0 0 0 0 0
    6 6 0 0 0 0 0 0 0
    6 0 0 0 0 0 0 0 0

I wonder if matlab has some neat function to plot the boundary of these sets generated by this matrix?

Answer 1

I think you are looking for a variation of contour plot. Don't forget that it will flip Y axis.

contour(M)
g = gca;
g.YDir = 'reverse';

for jj=1:size(M,1)
    for ii=1:size(M,2)
        text(jj,ii,num2str(M(ii,jj)));
    end
end