filename for genotypes, assumed IMPUTE verbose format.
phenotypes
if not null, a data frame of phenotypes to be merged with the
genotypes; first two columns will be used to match against first two
columns of the samplefile.
Value
Returns a list with snpinfo and data slots, see snpdata.
Details
This function needs better documentation.
This function will be slow for large input files. Best to use gtool
or grep/awk out the relevant lines (SNPs) into a smaller file first.