Will extract the mapping between IDs passed as `X` to function `poismf` and row/column positions in the latent factor matrices and prediction functions.
Such a mapping will only be generated if the `X` passed to `poismf` was a `data.frame`, otherwise they will not be re-mapped.
get.model.mappings(model)
A list with row entries:
`rows`: a vector in which each user/row ID is placed at its ordinal position in the internal data structures. If there is no mapping (e.g. if `X` passed to `poismf` was a sparse matrix), will be `NULL`.
`columns`: a vector in which each item/column ID is placed at its ordinal position in the internal data structures. If there is no mapping (e.g. if `X` passed to `poismf` was a sparse matrix), will be `NULL`.
A Poisson factorization model as returned by `poismf`.
get.factor.matrices