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#' function to download all available shapefile files from a URL
#' @import RCurl
#' @export
#' @examples
#' \dontrun{
#' download_shp('ftp://ftp.granit.sr.unh.edu/pub/GRANIT_Data/Vector_Data/Administrative_and_Political_Boundaries/d-nhsenatedists/2012','NHSenateDists2012')
#' download_shp('http://jwhollister.com/iale_open_science/files','LocPt')
#' }
download_shp <- function(shape_url, layer, outfolder = ".") {
if (length(grep("/$", shape_url)) == 0) {
shape_url <- paste(shape_url, "/", sep = "")
}
shapefile_ext <- c(".shp", ".shx", ".dbf", ".prj", ".sbn", ".sbx", ".shp.xml", ".fbn", ".fbx", ".ain",
".aih", ".ixs", ".mxs", ".atx", ".cpg")
xlogic <- NULL
if (substr(shape_url, 1, 3) == "ftp") {
xurl <- RCurl::getURL(shape_url)
for (i in paste(layer, shapefile_ext, sep = "")) {
xlogic <- c(xlogic, grepl(i, xurl))
}
} else if (substr(shape_url, 1, 4) == "http") {
for (i in paste(shape_url, layer, shapefile_ext, sep = "")) {
xlogic <- c(xlogic, httr::HEAD(i)$status == 200)
}
}
shapefiles <- paste(shape_url, layer, shapefile_ext, sep = "")[xlogic]
outfiles <- paste(outfolder, "/", layer, shapefile_ext, sep = "")[xlogic]
if (sum(xlogic) > 0) {
for (i in 1:length(shapefiles)) {
x <- suppressWarnings(httr::GET(shapefiles[i], httr::write_disk(outfiles[i], overwrite = TRUE)))
dwnld_file <- strsplit(shapefiles[i], "/")[[1]]
dwnld_file <- dwnld_file[length(dwnld_file)]
print(paste0("Downloaded ", dwnld_file, " to ", outfiles[i], "."))
}
} else {
stop("An Error has occured with the input URL or \n name of shapefile")
}
}