This function returns the columns requested from the column-wise splitted genetic/environmental data in ff format.
f.get.gen.data.cols(gen.data, cols, by.colname = FALSE)
Matrix (in ff format) with all the requested columns.
The list with genetic/environmental data (in ff format).
The sequence numbering (or listing) the columns which are to be retrieved; this should enumerate the columns as if all the data was in one large matrix.
Logical: is 'cols' given as a number sequence (FALSE, default) or character vector (TRUE) naming the columns to choose?