R/info.R

In nhdR: Tools for Working with the National Hydrography Dataset

#' Return NHD layer metadata and field listing
#'
#' @param state character
#' @param dsn character
#' @export
#' @return A column-wise summary of an sf read from the specfied layer
#'
#' @examples \dontrun{
#' nhd_info("DC", "NHDWaterbody")
#' }
nhd_info <- function(state, dsn) {
  summary(sf::st_read(gdb_path(state), layer = dsn, quiet = TRUE))
}

#' Return NHDplus layer metadata and field listing
#'
#' @param vpu numeric vector processing unit
#' @param component character component name
#' @param dsn character data source name
#' @param file_ext character choice of "shp" for spatial data and
#' "dbf" for non-spatial. optional
#' @export
#' @return A column-wise summary of an sf/foreign read from the specfied layer
#'
#' @examples \dontrun{
#' nhd_plus_info(vpu = 4, component = "NHDSnapshot", dsn = "NHDWaterbody")
#' nhd_plus_info(vpu = 1, component = "NHDPlusAttributes", dsn = "PlusFlow")
#' }
nhd_plus_info <- function(vpu, component, dsn, file_ext = NA) {
  candidate_files <- nhd_plus_list(vpu, component = component,
    full.names = TRUE, file_ext = file_ext)
  res <- candidate_files[grep(paste0(tolower(dsn), "\\."),
    tolower(candidate_files))]

  res <- res[grep(dsn, res)]

  if (length(grep(paste0("shp", "$"), res)) > 0) {
    res <- res[grep("shp$", res)]
    summary(sf::st_read(res, quiet = TRUE))
  } else {
    summary(foreign::read.dbf(res))
  }
}