Return array of thresholds corresponding to a probability of such value in the input
Thresholds are returned as an array with one value per column in the input
data.
Parameters:
data : 2D-array
Array with data on which the cumulative distribution is based.
Values in each column are sorted and the value corresponding to the
desired probability is returned.
p : float [0,1]
Value greater or equal than the returned threshold have a probability p or less.