about random again

I have one matrix as follows X = rand(4,10)

I want to generate a matrix from X and in each row a variable should be randomly selected and all possible combination can be used. actually the following code works for a small set like d = rand(4,3) but i have problem when a larger set like above X = rand(4,10) used , please run this and let me know .

[m,n] = size(x);
df = bsxfun(@plus,fullfact(m*ones(1,n)),(0:n-1)*m);
k = randperm(size(df,1));
out = x(df(k(1:min(100,numel(k))),:));

[Niki]

actually I have solved my problem in another way, but I am very interested to see how to amend this function

[Walter Roberson]

Perhaps you could describe the "problem" ?

[Niki]

Yes,

actually when I generate my matrix like for example follows

X = rand(10,23)

then i get the size of my matrix

[m,n] = size(X);

then I do

df = bsxfun(@plus,fullfact(m*ones(1,n)),(0:n-1)*m);

I will get error as

??? Error using ==> zeros

Maximum variable size allowed by the program is exceeded.

Error in ==> fullfact at 33

design = zeros(ssize,cols,class(levels));

Answer 1

[Walter Roberson]

If I calculate correctly, fullfact(m*ones(1,n)) creates m^n rows of output each of width n.

When X = rand(10,23) then you are asking for 10^23 rows each of width 23, and each element takes 8 bytes (double precision), so you are asking for (8*23) * 10^23 bytes of output. That would be about 2^84 bytes. That exceeds the largest variable that can be handled on a 64 bit operating system (2^64 bytes).

[Niki]

so what should I do to prevent such problem?

can you help me ?