Coerce parameters/data to a numeric matrix with a known column count

Preserves column names where they carry meaning: a data frame's or matrix's existing colnames, or a plain vector's names() when the vector is interpreted as a single row. A vector re-interpreted as a stacked column (the byrow branch) loses its names – they described entries, not a shared parameter/outcome identity.

Usage

as_theta_matrix(x, d = NULL)