Given the column indexing the appropriate cross-product and the total number of dimensions, find the two dimensions leading to the cross-product.
find_crossprod_dims(dim12, n_dims, init = 0L)the column of the matrix or data.frame
the total number of dimensions
an integer indicating the initial starting value for the set of integers included in the permutation. See Details.
A vector/array indicating the cross-product dimensions.
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.