Once input data is wrapped by the xform_wrap function, it is somewhat
involved to rename a variable inside. This function makes it easier to do
so. Given a variable named input_var and the name one wishes to
rename it to, output_var, the rename command options are:
xform_info="input_var -> output_var"
There are two methods in which the variables can be referred to. The first
method is to use its column number; given the data attribute of the
boxData object, this would be the order at which the variable
appears. This can be indicated in the format "column#". The second method is
to refer to the variable by its name. This method will work even if the
renamed value already exists; in which case there will be two variables with
the same name.
If no input variable name is provided, the original object is returned with
no renaming performed.