R/io.R

In JGCRI/rgis: R-based Geographic Information System (GIS) utilities

# Input/Output IO tools for rgis


#' Create an sf object from a shapefile
#'
#' Create an sf object from a full path to shapefile with file name and extension
#'
#' @param shp_path character. A full path to the input shapefile with file name and extension
#' @param quiet boolean.
#' @param method tool used to convert to spatial data; either 'sf' or 'rgdal'
#' @return sf object
#' @author Chris R. Vernon (chris.vernon@pnnl.gov)
#' @importFrom sf st_read
#' @importFrom rgdal readOGR
#' @export
import_shapefile <- function(shp_path, quiet = TRUE, method = "sf") {
  
  if(method == "sf") return(st_read(shp_path, quiet = quiet))
  if(method == "rgdal") return(readOGR(shp_path, verbose = !quiet))
}


#' Create a raster object from a file path
#'
#' Create a raster object from a full path to raster file name and extension
#'
#' @param raster_path character. A full path to the input raster file with file name and extension
#' @return raster object
#' @importFrom raster raster
#' @author Chris R. Vernon (chris.vernon@pnnl.gov)
#' @export
import_raster <- function(raster_path) {
  
  return(raster(raster_path))
}


#' Import NetCDF to brick raster
#'
#' Import NetCDF to brick raster
#'
#' @param ncdf_file character. A full path to the input NetCDF file with the file name and extension
#' @importFrom raster brick
#' @return raster object
#' @author Chris R. Vernon (chris.vernon@pnnl.gov)
#' @export
import_ncdf_to_raster <- function(ncdf_file) {
  
  return(brick(ncdf_file))
}


#' Import point data from a CSV file
#'
#' Import point data that contains a value to be spatially joined to the fishnet containing
#' fractional area.  May either be a shapefile or a CSV file containing a latitude and longitude
#' for each record.
#'
#' @param f character. The full path with filename and extension to the points dataset.
#' @param pts_lat_field character. The field name for latitude
#' @param pts_lon_field character. The field name for longitude
#' @param pts_crs int. The native EPSG number for the coordinate reference system used in the
#' creation of the input points data. The default is 4326 (WGS 1984).
#' @param my_crs int. The EPSG number of the desired coordinate reference system. The
#' default is EPSG:3857 the WGS 84 / Pseudo-Mercator -- Used by all modern web
#' mapping applications.
#' @importFrom sf st_as_sf st_transform
#' @return A simple features (sf) spatial data frame object.
#' @author Chris R. Vernon (chris.vernon@pnnl.gov)
#' @export
import_points_from_csv <- function(f, pts_lat_field, pts_lon_field, pts_crs = 4326, my_crs = 3857) {
  
  pts <- read.csv(file = f, header = TRUE, sep = ',')
  
  # change latitude, longitude columns to numeric
  cols.num <- c(pts_lat_field, pts_lon_field)
  pts[cols.num] <- sapply(pts[cols.num], as.numeric)
  
  # convert to sf spatial data frame object and transform to target CRS
  pts.SP <- st_as_sf(pts, coords = c(pts_lat_field, pts_lon_field), crs = pts_crs) %>%
    st_transform(crs = my_crs)
  
  return(pts)
}