Random sample without replacement

1 min readApr 2, 2022

Hi,all,

Does anybody know how to do random sample without replacement? The randsample function in matlab only supports sampling with replacement.

I made codes on my own, and it is really weird sometimes it works, but sometimes it shows error (Error using ==> randsample at 94 W must have length equal to N.):

function C=randsample_WithoutReplacement(m,n,A1,A2)
%A1:population 
%A2:probability
B=zeros(m,1);
C=zeros(n,m);
s=transpose(1:1:length(A1));
ut=0;
loc=0;A=A2;
for j=1:n    
    A=A2;
    s=transpose(1:1:length(A1));
    for i=1:m  
        B(i)=randsample(s,1,true,A);
        [ut, loc] = ismember(B(i), s);       
        s(loc)=[];
        A(loc)=[];
    end
    for i=1:m
        C(j,i)=A1(B(i));
    end    
end

NOTE:-

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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:

SEE COMPLETE ANSWER CLICK THE LINK