The concatenated input, as a cross
object. Additional
columns are added to the phenotype data indicating which cross an
individual comes from; another column indicates cross type (0=BC,
1=intercross), if there are crosses of different types. The crosses
are not required to have exactly the same set of phenotypes;
phenotypes with the same names are assumed to be the same.
If the crosses have different sets of markers, we
interpolate marker order, but the cM positions of markers that are in
common between crosses must be precisely the same in the different crosses.