public Dataframe getSubset(FlatDataList idsCollection) {
        Dataframe d = new Dataframe(configuration);

        for(Object id : idsCollection) {
            d.add(get((Integer)id));
        }
        return d;
    }
public Dataframe getSubset ( FlatDataList idsCollection ) { Dataframe d = new Dataframe ( configuration ) ; for ( Object id : idsCollection ) { d . add ( get ( ( Integer ) id ) ) ; } return d ; }
It generates and returns a new Dataframe which contains a subset of this Dataframe.
All the Records of the returned Dataframe are copies of the original Records.
The method is used for k-fold cross validation and sampling. Note that the
Records in the new Dataframe have DIFFERENT ids from the original ones.

@param idsCollection
@return