Generates histogram
pHist(X, p, nBins, freq = FALSE)a vector containing the data points
a vector containing the probabilities for each of the data points in X
expected number of Bins the data set is to be broken down into
a boolean variable to indicate whether the graphic is a representation of frequencies
a list with f the frequency for each midpoint x the midpoints of the nBins intervals
http://www.symmys.com See Meucci script pHist.m used for plotting