Given two dimension and the total number of dimensions, find the column indexing the appropriate cross-product.
find_crossprod_column(dim1, dim2, n_dims, init = 0L)the first dimension
the second dimension
the total number of dimensions
an integer indicating the initial starting value for the set of integers included in the permutation. See Details.
The index of the cross-product column.
init is useful for indexing C vs R code. If init = 0,
then the indices will work with 0 indexed languages, such as C or
Python. If init = 1, then the indices will work with 1 indexed
languages, such as R.
This function assumes that the first n_dims columns are the dims,
the next n_dims - 1 columns are the cross-products of dimension 1 with
the remaining dims, the next n_dims - 2 columns are the cross-products
of dimension 2 with the remaining dims > 2, etc.