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Problem of mathematics and programming

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Aaros
Aaros 2013-1-31
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?

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回答（5 个）

Walter Roberson
Walter Roberson 2013-1-31
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
Matt J 2013-1-31
编辑：Matt J 2013-1-31
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
Jonathan Epperl 2013-1-31
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
Aaros 2013-1-31
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
Youssef Khmou 2013-1-31
编辑：Youssef Khmou 2013-1-31
suppose your vector is
V=[0 0 0 0 0 1 1 1 1 1];
to find the positions you try :
[value,index]=find(V==0)

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