How do I store a maximum value from a 3-d matrix to a 2-d matrix?

I have a 3-d matrix z with variables x, y and s. I want to store the maximum value of z over s in a new matrix with variables x and y only. How should I do it?

if true
  % code
end
x = 1:32;
y = 1:32;
s = 1:20;
[X,Y,S]= ndgrid(x,y,s);
z= X.^2 + Y.^2 -2.*X.*S +Y.*S;
%Now how do I store maximum of z in a new matrix called zmax(x,y)%

Answer 1

[Walter Roberson]

zmax = min(z, [], 3);

[vishav Rattu]

Shouldn't it be max(z,[],3) and also will this matrix be a 2-d matrix?

[Walter Roberson]

Yes sorry max rather than min. The result will be 2d.