Benchmark and check the SpatialPolygons_to_geojson function based on Rcpp

benchmark_and_check_sptogeojson.R

# install newest geojsonio
devtools::install_github("ropensci/geojsonio")
# include the new function
source("https://gist.github.com/javrucebo/fbbfe4b504d49893ad03d8fe0bd84f73/raw/8cf2cc10ddef665ea8f1538e011fc6484e978cef/SpatialPolygons_to_geojson.R")

library(magrittr)
library(stringi)

# helper function: extract all numerical values from json string to check
# if values are nearly equal
xx_js2num <- function(str) {
  stri_match_all_regex(str, "(?<=[\\[,: {])([-+]?\\d+(?:\\.\\d+(?:[eE][-+]\\d+)?)?)") %>% extract2(1) %>% .[,1] %>% as.numeric
}
# helper function: substiture all numerical values by symbols to compare structure
xx_js_wo_num <- function(str) {
  # replace numbers by {NUM}"
  stri_replace_all_regex(str, "(?<=[\\[,: {])([-+]?\\d+(?:\\.\\d+(?:[eE][-+]\\d+)?)?)","{NUM}") %>%
    # add newline after each comma for later diffing
    stri_replace_all_fixed(",",",\n") %>%
    # eliminate spaces
    stri_replace_all_fixed(" ","") %>%
    # remove escape in front of '/' (as writeOGR introduces)
    stri_replace_all_fixed("\\/","/")
}

# compare to json strings whether they are "equal"
# a) extract all numerical values and calculate pairwise differences.
#    maximum absolute/relative difference 1e-4
# b) compare structure/strings without numerics
jsonstring_compare_pairwise <- function(x,y) {
  # extract numerical value
  x_num <- xx_js2num(x)
  y_num <- xx_js2num(y)
  # extract structure w/o nubers
  x_str <- xx_js_wo_num(x)
  y_str <- xx_js_wo_num(y)

  cat(x,file="/tmp/kkx")
  cat(y,file="/tmp/kky")
  cat(x_str,file="/tmp/jjx")
  cat(y_str,file="/tmp/jjy")

  # check whether structure is equal and numerical value close to each other
  check_num <- max(ifelse(y_num <1,abs(x_num-y_num),abs(x_num-y_num)/abs(y_num)))<1e-04
  check_str <- x_str == y_str
  if (!check_num) { message(paste("numeric difference",max(ifelse(y_num <1,abs(x_num-y_num),abs(x_num-y_num)/abs(y_num))))) }
  if (!check_str) { message("string difference") }
  check_num & check_str
}

# check values if they are nearly equal
jsonstring_compare <- function(values) {
  all(sapply(values[-1], function(x) jsonstring_compare_pairwise(values[[1]], x)))
}



## benchmark and check the functions
bench_sptogeojson <- function(sp, times=1) {
  sp::proj4string(sp) <- ""
  print(microbenchmark::microbenchmark(
  gejson_json=geojsonio::geojson_json(sp),
  SpatialPolygons_to_geojson=SpatialPolygons_to_geojson(sp),
  times=times,
  check=jsonstring_compare),
  unit="s", signif=3)
  invisible(sp)
}


bench_sptogeojson(raster::getData('GADM', country='VAT', level=0))
bench_sptogeojson(raster::getData('GADM', country='UKR', level=1))
bench_sptogeojson(raster::getData('GADM', country='SWE', level=2))
bench_sptogeojson(raster::getData('GADM', country='CAN', level=3))