constraints on the rows and columns of a matrix [duplicate]

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• Controlled random number/dataset generation in MATLAB 2 answers

I would like to create a mxn matrix of random values in MATLAB. The constraints are that each element of a column must be lower than or equal to a fix constant and each row must sum to one. I've just coded for this matrix by "for" and "while" scripts which is trapped in the loop. May you please guide me.

Thanks in advance