# Problem of mathematics and programming

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Aaros on 31 Jan 2013
Suppose I have an array stored 50 data, data are just '0' and '1' The probability of occurrence of '0' is 0.1 The probability of occurrence of '1' is 0.9
So there are five '0' and forty-five '1' and suppose the five '0' are appeared first.
The sequence is :{0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,.....,1}
I want to find out all the sequenes which the '0' are located at different position.
ie: the five '0' are placed at every different locations
Can matlab function solve this question? how to implement to solve this?
Youssef Khmou on 31 Jan 2013
[value,index]=find(VECTOR==0)

Walter Roberson on 31 Jan 2013
Are you looking for the permutations of the array? There would be (50!) / ((45!)*(5!)) = 2118760 of them. What are you going to do with them after you find them all?

Matt J on 31 Jan 2013
Edited: Matt J on 31 Jan 2013
x=[0 0 0 0 0, ones(1,45)];
idx=nchoosek(1:50,5);
rows=repmat((1:size(idx,1)).',[1,5]);
result = ~full(sparse(rows,idx,true));

Jonathan Epperl on 31 Jan 2013
Like Walter said, what you are ultimately looking for are all the combinations you obtain from drawing 5 out of 50 without replacement, so nchoosek(50,5). Matlab will give you a matrix where each row is one combination
M = nchoosek(1:50,5);
You'll get your 0s and 1s then by (and I'm sure there are better ways):
M = nchoosek(1:50,5);
Z = ones(10,size(M,1));
MM = M + (0:size(M,1)-1)'*10*ones(1,size(M,2));
Z(MM)=0;
imagesc(Z')

Aaros on 31 Jan 2013
i need to use those sequences to be a fault vector.
also, the probability will be changed, the number of '0' will increase or decrease

Youssef Khmou on 31 Jan 2013
Edited: Youssef Khmou on 31 Jan 2013
V=[0 0 0 0 0 1 1 1 1 1];
to find the positions you try :
[value,index]=find(V==0)