HISTO2 calculates histogram of each column
R=HISTO2(Y)

R=HISTO(...)
R is a struct with th fields
R.X  are the bin-values
R.H  is the frequency of occurence of value X
R.N  are the number of valid (not NaN) samples

more histogram-based results can be obtained by HIST2RES2

see also: HISTO, HISTO2, HISTO3, HISTO4

REFERENCE(S):
C.E. Shannon and W. Weaver "The mathematical theory of communication" University of Illinois Press, Urbana 1949 (reprint 1963).