subvariables
a list of Variable objects to bind together, or a
Dataset object containing only the Variables to bind (as in from subsetting
a Dataset), or values (e.g. names) of variables corresponding to key.
If omitted, must supply dataset and pattern. If specifying
values, must include dataset.
dataset
the Crunch Dataset to which the variables in
subvariables belong, or in which to search for variables based
on pattern. If omitted, subvariables must exist and all
Variables in the list must belong to the same Dataset