Plot a matrix, values as colors

Question

I have random matrix with arbitrary dimensions and I want to assign a color for each value (randomly or not) and plot the matrix with numbers like,

Answer 1

Using imagesc instead of pcolor solves the problem. It also brings some other benefits:

• Avoids the need for flipud;
• The coordinates of the text objects become integer values;
• Axes are automatically set to "matrix" mode, with the origin in the upper right corner.

Code:

m = 8;
n = 6;
A = randi(5,[m n]);
imagesc(A);
for ii = 1:n
    for jj = 1:m
        text(ii, jj, num2str(A(jj,ii)), 'FontSize', 18);
    end
end

For

A =
     4     5     4     2     4     4
     5     4     3     4     4     2
     5     4     1     1     1     3
     4     3     5     2     5     4
     1     2     2     2     5     3
     1     5     2     5     1     3
     4     3     1     3     3     1
     3     1     2     4     2     3

this produces

Answer 2

I just padded the matrix prior to pcolor and I think it's the effect you wanted. The reason it works comes from the help doc for pcolor, which states that

In the default shading mode, 'faceted', each cell has a constant color and the last row and column of C are not used.

m = 12;
n = 8;
A = randi(5,[m n]);
Arot = flipud(A);
Arot = [ Arot; Arot(end,:) ];
Arot = [ Arot, Arot(:,end) ];
pcolor(Arot);figure(gcf);
for i = 1 : n
  for j = 1 : m
    text(i + .5 , j + .5 ,num2str(Arot(j,i)),'FontSize',18);
  end
end