Generating a random binary matrix with conditions

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Christy Jackson 2016-8-5

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评论： Image Analyst 2016-8-5

采纳的回答： John D'Errico

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Hello

I have written the following line of code to generate a random binary matrix

Pop = round(rand(5,5))

It works fine in most cases however sometimes i get columns with all zeros, how do i avoid getting all zeros in any of the column.

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John D'Errico 2016-8-5

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Just throw those columns away, if you get any like that, and replace them with new samples. WTP?

Thats true john, but i use this line of code for running in generations upto 500 and in each generation i might use a matrix of 100x100 or even more. So as the matrix size increase i tend to get more number of columns affecting my final output.

Guillaume 2016-8-5

编辑：Guillaume 2016-8-5

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But as the size of the matrix increases, the likelihood of getting a whole column of zero decreases (dramatically!), so John answer is even more valid.

The likelyhood of getting a whole column of zero in a 100x100 matrix is 100/2^100 ~ 1 in 1e28. In the very unlikely event that it happens, it takes microseconds to generate a new 100x100 matrix.

>> tic;randi([0 1], 100);toc
Elapsed time is 0.000363 seconds.

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Azzi Abdelmalek 2016-8-5

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A=zeros(5)
[n,m]=size(A)
for k=1:m
  id=randperm(n,randi(n))
  A(k,id)=1
end

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Christy Jackson 2016-8-5

Thats pretty much it steven, sorry about that..!!

Image Analyst 2016-8-5

Are there no restrictions on the number of "true" points in the array? Or is any number of them okay? Do you specifically want 5000 in a 100x100, or do you want an average of 30% of them to be true? Or any other criteria? Whether you realize it or not, you are specifying the fraction of points, at least on average. Like doing round() will say that on average 50% of them will be true, but it doesn't have to be 50% - it can be anything you want it to be.

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