empirical cumulative function
[F,X] = nan_ecdf(Y) nan_ecdf(Y) nan_ecdf(gca,Y) nan_ecdf(...,'plot')
input data, must be a vector or matrix, in case Y is a matrix, the ecdf for every column is computed.
if one input parameter is 'plot', it plots the empirical cdf, in axis gca.
empirical cumulative distribution functions (i.e Kaplan-Meier estimate)
NaN's are considered Missing values and are ignored.