R/get_mml.R

In rOpenGov/gisfin: Finland GIS R Tools

#' @title Get MML (Land Survey Finland) data
#' @description Retrieve data from Land Survey Finland (Maanmittauslaitos, MML). The data are processed into .RData files due to their big size. See the preprocessing details in \url{https://github.com/avoindata/mml}.
#' @param map.id data ID. See details.
#' @param data.id data ID. See details.
#' @param verbose logical. Should R report extra information on progress? 
#' @return url connection
#' @details To browse for available RData, run list_mml_datasets() or see https://github.com/avoindata/mml/tree/master/rdata. 
#' @export
#' @author Leo Lahti \email{louhos@@googlegroups.com}
#' @references See citation("gisfin") 
#' @examples datasets <- list_mml_datasets(); 
#'           map.id <- names(datasets)[[4]]; 
#'           data.id <- datasets[[map.id]][[1]]; 
#'           sp <- get_mml(map.id, data.id)
get_mml <- function(map.id, data.id, verbose = TRUE) {

  # DO NOT SET sp <- NULL HERE; this will return NULL for the function
  # IN CONTRAST TO INTENDED OUTPUT!!!
  sp <- NULL	

  #url <- paste(ropengov_storage_path(), "mml/rdata/", sep = "")
  #url <- "https://github.com/avoindata/mml/tree/master/rdata/"
  url <- "https://github.com/avoindata/mml/blob/master/rdata/"

  filepath <- paste(url, map.id, "/", data.id, ".RData?raw=true", sep = "")
  # Yleiskartta-4500/HallintoAlue.RData

  if (verbose)
    message("Loading ", filepath, ". (C) MML 2013. Converted to RData shape object by Louhos. For more information, see https://github.com/avoindata/mml/")

  # Direct downloads from Github:
  # library(RCurl)
  # dat <- read.csv(text=getURL("link.to.github.raw.csv"))

  #load(url(filepath), envir = .GlobalEnv) # Returns a shape file sp
  load(url(filepath)) # Returns a shape file sp
  
  if (verbose)
    message("\nData loaded successfully!")
  return(sp)
}