selecting random values

I have a matrix of 10x10

i want to select random values such that my matrix form should be 3x3 or 6x6 or 7x7

please help

[Walter Roberson]

In the 3x3 (say), do all of the elements in the same row of the result have to have come from the same row in the original matrix? And for the columns? So should the selection be of N rows against N columns?

Answer 1

[Andrei Bobrov]

A = randi(48,3,10)

n = 3;
q = reshape(1:numel(A),n,[]);
rc = size(A)- n +1;
m = q(1:rc(1),1:rc(2));
p = m(randperm(numel(m),1));
out = A(rem(p-1,n(1))+(1:n(1)),ceil(p/n(1))+(0:n(2)-1))

OR

A = randi(48,10)
n = [4,6];
i1 = arrayfun(@(x)randi( size(A,x)- n(x) + 1) + (0:n(x)-1),1:2,'un',0);
out = A(i1{:})