R/get_shp_zip.R

In ryanpeek/wateRshedTools: Watershed Tools For Datetime Data

# get zipped shp
#' Read a zipped shapefile
#'
#' This function takes a \emph{path} to a given shapefile
#' from online or local directory, and
#' returns a \emph{sf} based data.frame to the R environment.
#'
#' @param shp_url A character path to a zipped shapefile, locally or online.
#' @param web TRUE/FALSE, is the path a web URL or a local directory path
#' @return Returns an sf data.frame.
#' @importFrom utils download.file
#' @importFrom mapview mapview
#' @examples
#' # set up the parameters to use in function:
#' library(sf)
#' library(utils)
#' library(mapview)
#'
#' # get a shapefile of all USGS gages in North America
#' shp_url <- "https://water.usgs.gov/GIS/dsdl/gagesII_9322_point_shapefile.zip"
#'
#' gages2 <- get_shp_zip(shp_url)
#'
#' # now plot
#' mapview::mapview(gages2)

#' @export
get_shp_zip <- function(shp_url, web=TRUE){
    dest_dir <- tempdir() # make temp dir
    temp_shp <- tempfile(tmpdir = dest_dir) # make tempfile for shp
    if(web){
      download.file(shp_url,temp_shp) # download the zipped file
      if( grepl('.tgz$|.tar.gz$', shp_url) ){
        utils::untar(temp_shp, exdir = dest_dir)
      } else if(grepl('.zip$', shp_url)){
        utils::unzip(temp_shp, exdir = dest_dir)
      } else{
        stop('not *.zip or *.tgz or *.tar.gz!')
      }
    } else {
      # just unzip from path given
      print("just using direct url as path")
      # now unzip the file depending on extension
      if( grepl('.tgz$|.tar.gz$', shp_url) ){
        utils::untar(shp_url, exdir = dest_dir)
      } else if(grepl('.zip$', shp_url)){
        utils::unzip(shp_url, exdir = dest_dir)
      } else{
        stop('not *.zip or *.tgz or *.tar.gz!')
      }
    }
    # now get shp name with full temp path
    shp_file <- list.files(dest_dir, pattern = ".shp$", full.names=TRUE)
    # read it in!
    sf::st_read(shp_file)
    # when we close the R session, the temp dir/files are removed!
  }