add cpp code

DESCRIPTION

@@ -12,15 +12,18 @@ Description: The concaveman function ports the 'concaveman' (<https://github.com
 License: GPL-3
 Encoding: UTF-8
 LazyData: true
+NeedsCompilation: yes
 Roxygen: list(markdown = TRUE)
 Depends: R (>= 2.10)
-Imports: V8, 
+Imports: V8,
          sf, 
          magrittr,
          jsonlite,
-         dplyr
+         dplyr,
+         Rcpp
 RoxygenNote: 7.1.0
 Suggests: testthat
+LinkingTo: Rcpp
 URL: https://joelgombin.github.io/concaveman, http://www.github.com/joelgombin/concaveman
 BugReports: http://www.github.com/joelgombin/concaveman/issues
-SystemRequirements: GDAL (>= 2.0.0), GEOS (>= 3.3.0), PROJ.4 (>= 4.8.0)
+SystemRequirements: C++11, GDAL (>= 2.0.0), GEOS (>= 3.3.0), PROJ.4 (>= 4.8.0)

NAMESPACE

@@ -3,4 +3,7 @@
 S3method(concaveman,matrix)
 S3method(concaveman,sf)
 export(concaveman)
+export(concaveman_rcpp)
+importFrom(Rcpp,evalCpp)
 importFrom(magrittr,"%>%")
+useDynLib(concaveman, .registration = TRUE)

R/RcppExports.R

@@ -0,0 +1,9 @@
+# Generated by using Rcpp::compileAttributes() -> do not edit by hand
+# Generator token: 10BE3573-1514-4C36-9D1C-5A225CD40393
+
+#' rcpp_concaveman_mat
+#' @noRd 
+rcpp_concaveman_mat <- function(xy, hull_in, concavity, length_threshold) {
+    .Call(`_concaveman_rcpp_concaveman_mat`, xy, hull_in, concavity, length_threshold)
+}
+

R/concaveman-pkg.R

@@ -3,6 +3,8 @@
 #' This package is a simple R port (through [`V8`](https://github.com/jeroen/v8)) of a [JavaScript library by Vladimir Agafonkin](https://github.com/mapbox/concaveman).
 #'
 #'
+#' @importFrom Rcpp evalCpp
+#' @useDynLib concaveman, .registration = TRUE
 #' @docType package
 #' @name concaveman
 NULL

R/concaveman.R

@@ -54,3 +54,12 @@ concaveman.sf <- function(points, concavity = 2, length_threshold = 0) {
               )
 }
 
+#' concaveman_rcpp
+#'
+#' @export
+#' @rdname concaveman_rcpp
+concaveman_rcpp <- function (xy, concavity = 2, length_threshold = 0) {
+    index <- grDevices::chull (xy)
+    index <- c (index, index [1])
+    rcpp_concaveman_mat (xy, index - 1, concavity, length_threshold)
+}