Not meant to be called directly by the user.
check.whatmap(x, whatmap)A kohonen object, or a
list of data matrices that can be used as input data for SOM functions.
An indication of a subset of the data; either by naming
the elements, or giving indices. If whatmap equals NULL, the
selection of x is used if x is a kohonen
object, or else no selection is performed.
Returns a numerical vector with the indices of the selected layers. An invalid selection leads to an error.