#' MeSH Descriptor Frequencies Across PubMed
#'
#' Baseline frequencies for MeSH descriptors computed from a local PostgreSQL
#' mirror of PubMed (April 2026). For each descriptor, counts reflect the
#' number of distinct PMIDs indexed with that term; proportions use the full
#' PubMed corpus of 39,703,112 PMIDs as denominator. Descriptor UI and
#' canonical name are joined from the NLM MeSH thesaurus.
#' Intended as a baseline for MeSH term enrichment analyses against arbitrary
#' PubMed subsets.
#'
#' @format A data.table with 30,521 rows and 4 columns:
#' \describe{
#'   \item{DescriptorUI}{MeSH descriptor unique identifier (e.g.,
#'     \code{D000001})}
#'   \item{DescriptorName}{Canonical MeSH descriptor name}
#'   \item{n_pmids}{Number of distinct PubMed records indexed with this
#'     descriptor}
#'   \item{prop_total}{Proportion of all 39,703,112 PubMed PMIDs indexed
#'     with this descriptor}
#' }
#' @source Computed from \code{mesh_descriptor} table in a local PubMed
#'   PostgreSQL mirror; descriptor metadata from the NLM MeSH Thesaurus
#'   (April 2026).
"data_mesh_frequencies"
