Random sample without replacement

Here is a recursive function that will return one row of your matrix C:

function y = randsampleWithoutReplacement(population,k,w)

y = [];
if ~isempty(population) && k > 0
  n = length(population);
  ii = randsample(1:n,1,true,w);
  newpop = setdiff(1:n,ii);
  y = [population(ii) randsampleWithoutReplacement(population(newpop),k-1,w(newpop))];
end

and here is an example of a call:

y = randsampleWithoutReplacement(1:100,20,ones(100,1)/100)

EDIT: And here is one that is closer to your version:

function C=randsample_WithoutReplacement(A1,k,A2)
%A1:population 
%A2:probability
C=zeros(1,k);
A=A2;
n = length(A1);
for i=1:k
  loc=randsample(n-i+1,1,true,A);
  A(loc)=[];
  C(i)=A1(loc);
end

However, I have designed it to act more like randsample.