QUANTILE

quantile
Empirical quantile (percentile).

         q = quantile(x,p)
	Input	x	vector or matrix of reals
		p	probability (scalar or vector of probabilities numbers)

	Output	q 	the empirical quantile of the sample x, a value
			that is greater than p percent of the values in x
	  		If input x is a matrix then the quantile is 
			computed for  every column. 
			If p is a vector then q is a matrix, each line contain 
			the quantiles  computed for a value of p
			 
	  The empirical quantile is computed by one of three ways
	  determined by a third input argument (with default 1).

	  1. Interpolation so that F(X_(k)) == (k-0.5)/n.
	  2. Interpolation so that F(X_(k)) == k/(n+1).
	  3. Based on the empirical distribution.