description: kstest applies the Kolmogorov-Smirnov test to two columns of
data, one from each of two files, to determine the probability that
the columns are drawn from the same distribution.
files: filename1 and filename2 are the names of the files from which the two columns
of data are drawn.
options:
first, second
Specify, respectively for filename1 and filename2, whether to use the abscissae ( x) or ordinates.
By default the ordinates from both files are used.