Add a radius argument to find_snap()

java-r5rcore/src/org/ipea/r5r/R5RCore.java

@@ -522,17 +522,18 @@ public double[] testDecay(String decayFunctionName, double decayValue) {
     }
 
     // ----------------------------------  FIND SNAP POINTS  -----------------------------------------
-    public RDataFrame findSnapPoints(String fromId, double fromLat, double fromLon, String mode) throws ExecutionException, InterruptedException {
+    public RDataFrame findSnapPoints(String fromId, double fromLat, double fromLon, double radius, String mode) throws ExecutionException, InterruptedException {
         String[] fromIds = {fromId};
         double[] fromLats = {fromLat};
         double[] fromLons = {fromLon};
 
-        return findSnapPoints(fromIds, fromLats, fromLons, mode);
+        return findSnapPoints(fromIds, fromLats, fromLons, radius, mode);
     }
 
-    public RDataFrame findSnapPoints(String[] fromId, double[] fromLat, double[] fromLon, String mode) throws ExecutionException, InterruptedException {
+    public RDataFrame findSnapPoints(String[] fromId, double[] fromLat, double[] fromLon, double radius, String mode) throws ExecutionException, InterruptedException {
         SnapFinder snapFinder = new SnapFinder(r5rThreadPool, this.transportNetwork);
         snapFinder.setOrigins(fromId, fromLat, fromLon);
+        snapFinder.setRadius(radius);
         snapFinder.setMode(mode);
         return snapFinder.run();
     }

java-r5rcore/src/org/ipea/r5r/SnapFinder.java

@@ -22,8 +22,13 @@ public class SnapFinder {
     protected String[] fromIds;
     protected double[] fromLats;
     protected double[] fromLons;
+    protected double radius;
     private StreetMode mode;
 
+    public void setRadius(double radius) {
+        this.radius = radius;
+    }
+
     public void setMode(String mode) {
         this.mode = StreetMode.valueOf(mode);
     }
@@ -61,8 +66,7 @@ public RDataFrame run() {
             snapTable.set("lat", fromLats[index]);
             snapTable.set("lon", fromLons[index]);
 
-            Split split = transportNetwork.streetLayer.findSplit(fromLats[index], fromLons[index],
-                    StreetLayer.LINK_RADIUS_METERS, this.mode);
+            Split split = transportNetwork.streetLayer.findSplit(fromLats[index], fromLons[index], this.radius, this.mode);
 
             if (split != null) {
                 // found split at StreetLayer.INITIAL_LINK_RADIUS_METERS

r-package/R/find_snap.R

@@ -6,20 +6,22 @@
 #' created by `R5`. The snapping process in `R5` is composed of two rounds.
 #' First, it tries to snap the points within a radius of 300 meters from
 #' themselves. If the first round is unsuccessful, then `R5` expands the search
-#' radius to 1.6 km. If yet again it is unsuccessful, then the unsnapped points
-#' won't be used during the routing process. The snapped location of each point
-#' depends on the transport mode set by the user, because some network edges
-#' are not available to specific modes (e.g. a pedestrian-only street cannot be
-#' used to snap car trips).
+#' to the radius specified (by default 1.6km). If yet again it is unsuccessful,
+#' then the unsnapped points won't be used during the routing process. The
+#' snapped location of each point depends on the transport mode set by the user,
+#' because some network edges are not available to specific modes (e.g. a
+#' pedestrian-only street cannot be used to snap car trips).
 #'
 #' @template r5r_core
 #' @param points Either a `POINT sf` object with WGS84 CRS, or a `data.frame`
 #' containing the columns `id`, `lon` and `lat`.
+#' @param radius Numeric. The maximum radius in meters within which to snap.
+#' Defaults to 1600m.
 #' @param mode A string. Which mode to consider when trying to snap the points
 #' to the network. Defaults to `WALK`, also allows `BICYCLE` and `CAR`.
 #'
 #' @return A `data.table` with the original points, their respective
-#' snapped coordinates on the street network and the Euclidean distance ( in
+#' snapped coordinates on the street network and the Euclidean distance (in
 #' meters) between the original points and their snapped location. Points that
 #' could not be snapped show `NA` coordinates and `found = FALSE`.
 #'
@@ -32,14 +34,15 @@
 #' r5r_core <- setup_r5(data_path = path)
 #' points <- read.csv(file.path(path, "poa_hexgrid.csv"))
 #'
-#' snap_df <- find_snap(r5r_core, points, mode = "WALK")
+#' snap_df <- find_snap(r5r_core, points, radius = 2000, mode = "WALK")
 #'
 #' stop_r5(r5r_core)
 #' @export
-find_snap <- function(r5r_core, points, mode = "WALK") {
+find_snap <- function(r5r_core, points, radius = 1600, mode = "WALK") {
   checkmate::assert_class(r5r_core, "jobjRef")
 
   mode_options <- c("WALK", "BICYCLE", "CAR")
+  checkmate::assert_numeric(radius, lower = 0, finite = TRUE, max.len = 1)
   checkmate::assert(
     checkmate::check_string(mode),
     checkmate::check_names(mode, subset.of = mode_options),
@@ -48,7 +51,11 @@ find_snap <- function(r5r_core, points, mode = "WALK") {
 
   points <- assign_points_input(points, "points")
 
-  snap_df <- r5r_core$findSnapPoints(points$id, points$lat, points$lon, mode)
+  snap_df <- r5r_core$findSnapPoints(points$id,
+                                     points$lat,
+                                     points$lon,
+                                     radius,
+                                     mode)
   snap_df <- java_to_dt(snap_df)
 
   snap_df[found == FALSE, `:=`(snap_lat = NA, snap_lon = NA, distance = NA)]

r-package/tests/testthat/test-find_snap.R

@@ -17,6 +17,9 @@ test_that("adequately raises errors", {
   # invalid points
   expect_error( find_snap(r5r_core=r5r_core, points = 'a', mode = 'WALK') )
 
+  # invalid radius
+  expect_error( find_snap(r5r_core=r5r_core, points = 'a', radius = -90, mode = 'WALK') )
+
 })
 
 
@@ -26,6 +29,20 @@ test_that("adequately raises errors", {
 test_that("output is correct", {
 
   # expected behavior
-  expect_s3_class( find_snap(r5r_core, points = points, mode = 'WALK'), 'data.table' )
+  expect_s3_class( find_snap(r5r_core=r5r_core, points = points, mode = 'WALK'), 'data.table')
+
+  # 6 points don't get snapped using the default radius after moving them
+  points_snap <- points
+  points_snap$lat <- points_snap$lat + 0.01
+  expect_equal(
+    sum(!find_snap(r5r_core, points_snap, mode = 'WALK')$found),
+    6
+  )
+
+  # all points are snapped after increasing the radius
+  expect_equal(
+    sum(!find_snap(r5r_core, points_snap, mode = 'WALK', radius = 5000)$found),
+    0
+  )
 
 })