Random sample without replacement

Random sample with weight and without replacement

% Random smapling with weight and without replacement
% O/P : sample--> random sample
% I/P : N--> population; n--> sample size; W--> weightage vector

function sample = RandSampleWR(N,n,W)
%% checking
if(length(N)<=0)||(n<=0)||(length(N)<=n)
disp('Populationsize and sample size must be greater than zero and sample size must be less than population size.')
close
end
if (length(N) ~= length(W))
disp('Population size and weightage vector size must be same.')
close
end
%% initialization
maxN = length(N);
k = 1;
W = W/sum(W(1:maxN));
%% Knuth-Fisher-Yates sampling
for i=n:-1:1
r1 = ceil(rand*maxN);
r2 = rand;
while(r2>W(r1))
r1 = ceil(rand*maxN);
r2 = rand;
end
sample(k) = N(r1);
temp = N(maxN);
temp1 = W(r1);
temp2 = W(maxN);
N(maxN) = sample(k);
N(r1) = temp;
W(maxN) = temp1;
W(r1) = temp2;
maxN = maxN-1;
W = W/sum(W(1:maxN));
k = k+1;
clear temp temp1 temp2 r1 r2
end