How to place a number in a random position in a matrix of zeros?
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I have a matrix "m" of zeros(6,7) and I would like to know how to place a variable equaling 1 into a random spot in the matrix. For example, the "1" could be randomly placed in m(1,2) or m(5,4), etc. How would I code this to pick a random row and random column?
Thank you for your help!
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Accepted Answer
Star Strider
on 28 Apr 2017
Edited: Star Strider
on 28 Apr 2017
I would use linear indexing, taking advantage of how matrices are stored in MATLAB, to use one number to define both the row and column:
M = zeros(6,7);
M(randi(numel(M))) = 1
M =
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 1 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
EDIT — You can do this with more lines of code, creating the linear index in one line, and using the ind2sub function to return the subscripts.
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R. Pam
on 14 Apr 2020
Hey, this is very helpful. Thanks. But what if I want the vector to be randomly shown as a row or a column? I'm quite confused, is it possible?
Star Strider
on 14 Apr 2020
@R. Pam — It is possible. As I mentioned, it would be necessary to make the appropriate changes in the ind2sub call, reflecting the orientation (row or column) of the vector you want to insert. It would also be necessary to add code to check the sizes of the vector and the matrix to limit the initial index appropriately.
I leave that to you.
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