Generate Only a Specific Number of Combinations

I would like to loop through the combinations of 30 take 20 with no repetition and order does not matter. I would only like to compute the first 100 or so combinations as there are over 30,000,000 total combinations. Is there a MatLab function that will allow me to do this? Functions like nchoosek will generate all possible combinations and take a very long time.

[Matt J]

What do you mean by the "first 100..."? How in your mind are the combinations ordered?

[Nicholas]

Order does not really matter. Any set of 100 will do.

Answer 1

[Matt Fig]

There are several functions on the FEX that do something like this. For instance:

NEXTPERMUTATION/COMBINATION

One could also make an index into the set by something like this:

A = [88 44 55 66 33 22 11 99 77 66];
idx = randperm(10,4);
A(idx) %  A random sampling of 4 elements of A

So you do this in a loop as many times as needed, storing all the idx values and checking for uniqueness, then after the loop you have the needed random samplings.

Answer 2

[Matt J]

This will generate 120 combinations

A=nchoosek(10,1:3);
N=size(A,1);
Result=[A,repmat(11:27,N,1)];