Generate random integers given probability distribution

The code generates the random integers for the probability distribution (probability mass function (PMF)) defined by the vector.

pmfRND Ouputs random integers for given PMF

x = pmfRND(f,X) returns mxn matrix whose values are Zipf distributed,
where f > 0 is the PMF (discrete PDF) such that sum(f) = 1;
X = [m,n] is the size of desired ouput random matrix.