An object of class cross. See
read.cross for details.
filestem
A character string giving the first part of the output
file names (the bit before the dot).
chr
A vector specifying for which chromosomes data should be
written.
digits
Number of digits to which phenotype values should be
rounded.
Value
Data is written to two files, in mapmaker format. Suppose
filestem="file". Then "file.raw" will contain the genotype and
phenotype data, and "file.prep" will contain the necessary code for
defining the chromosome assignments, marker order, and inter-marker
distances.