Merge branch 'project'

NAMESPACE

@@ -461,7 +461,9 @@ export(st_jitter)
 export(st_join)
 export(st_layers)
 export(st_length)
+export(st_line_interpolate)
 export(st_line_merge)
+export(st_line_project)
 export(st_line_sample)
 export(st_linestring)
 export(st_m_range)

NEWS.md

@@ -1,3 +1,7 @@
+# version 1.0-16
+
+* add `st_line_project()` to find how far a point is when projected on a line, and `st_line_interpolate()` to obtain a point at a certain distance along a line; #2291
+
 # version 1.0-15
 
 * add `st_perimeter()` to cover both geographic and projected coordinates; #268, #2279, by @JosiahParry

R/RcppExports.R

@@ -249,6 +249,14 @@ CPL_nary_intersection <- function(sfc) {
     .Call(`_sf_CPL_nary_intersection`, sfc)
 }
 
+CPL_line_project <- function(lines, points, normalized) {
+    .Call(`_sf_CPL_line_project`, lines, points, normalized)
+}
+
+CPL_line_interpolate <- function(lines, dists, normalized) {
+    .Call(`_sf_CPL_line_interpolate`, lines, dists, normalized)
+}
+
 CPL_hex_to_raw <- function(cx) {
     .Call(`_sf_CPL_hex_to_raw`, cx)
 }

R/geom-measures.R

@@ -211,3 +211,52 @@ st_distance = function(x, y, ..., dist_fun, by_element = FALSE,
 		d
 	}
 }
+
+check_lengths = function (dots) {
+	lengths <- vapply(dots, length, integer(1))
+	non_constant_lengths <- unique(lengths[lengths != 1])
+	if (length(non_constant_lengths) == 0) {
+		1
+	}
+	else if (length(non_constant_lengths) == 1) {
+		non_constant_lengths
+	}
+	else {
+		lengths_label <- paste0(non_constant_lengths, collapse = ", ")
+		stop(sprintf("Incompatible lengths: %s", lengths_label), 
+			call. = FALSE)
+	}
+}
+
+recycle_common = function (dots) {
+	final_length <- check_lengths(dots)
+	lapply(dots, rep_len, final_length)
+}
+
+
+#' Project point on linestring, interpolate along a linestring
+#'
+#' Project point on linestring, interpolate along a linestring
+#' @param line object of class `sfc` with `LINESTRING` geometry
+#' @param point object of class `sfc` with `POINT` geometry
+#' @param normalized logical; if `TRUE`, use or return distance normalised to 0-1
+#' @name st_line_project_point
+#' @returns `st_line_project` returns the distance(s) of point(s) along line(s), when projected on the line(s)
+#' @export
+#' @details
+#' arguments `line`, `point` and `dist` are recycled to common length when needed
+#' @examples
+#' st_line_project(st_as_sfc("LINESTRING (0 0, 10 10)"), st_as_sfc(c("POINT (0 0)", "POINT (5 5)")))
+#' st_line_project(st_as_sfc("LINESTRING (0 0, 10 10)"), st_as_sfc("POINT (5 5)"), TRUE)
+st_line_project = function(line, point, normalized = FALSE) {
+	stopifnot(inherits(line, "sfc"), inherits(point, "sfc"),
+		all(st_dimension(line) == 1), all(st_dimension(point) == 0),
+		is.logical(normalized), length(normalized) == 1,
+		st_crs(line) == st_crs(point))
+	line = st_cast(line, "LINESTRING")
+	point = st_cast(point, "POINT")
+	if (isTRUE(st_is_longlat(line)))
+		message_longlat("st_project_point")
+	recycled = recycle_common(list(line, point))
+	CPL_line_project(recycled[[1]], recycled[[2]], normalized)
+}

R/geom-transformers.R

@@ -1121,3 +1121,22 @@ st_line_sample = function(x, n, density, type = "regular", sample = NULL) {
 	if (length(pts) == 2 && is.numeric(pts))
   		assign(".geos_error", st_point(pts), envir=.sf_cache)
 } #nocov end
+
+#' @param dist numeric, vector with distance value(s)
+#' @name st_line_project_point
+#' @returns `st_line_interpolate` returns the point(s) at dist(s), when measured along (interpolated on) the line(s)
+#' @export
+#' @examples 
+#' st_line_interpolate(st_as_sfc("LINESTRING (0 0, 1 1)"), 1)
+#' st_line_interpolate(st_as_sfc("LINESTRING (0 0, 1 1)"), 1, TRUE)
+st_line_interpolate = function(line, dist, normalized = FALSE) {
+	stopifnot(inherits(line, "sfc"), all(st_dimension(line) == 1), 
+		is.logical(normalized), length(normalized) == 1,
+		is.numeric(dist))
+	if (isTRUE(st_is_longlat(line)))
+		message_longlat("st_project_point")
+	line = st_cast(line, "LINESTRING")
+	recycled = recycle_common(list(line, dist))
+	st_sfc(CPL_line_interpolate(recycled[[1]], recycled[[2]], normalized), 
+		   crs = st_crs(line))
+}

src/RcppExports.cpp

@@ -858,6 +858,32 @@ BEGIN_RCPP
     return rcpp_result_gen;
 END_RCPP
 }
+// CPL_line_project
+Rcpp::NumericVector CPL_line_project(Rcpp::List lines, Rcpp::List points, bool normalized);
+RcppExport SEXP _sf_CPL_line_project(SEXP linesSEXP, SEXP pointsSEXP, SEXP normalizedSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< Rcpp::List >::type lines(linesSEXP);
+    Rcpp::traits::input_parameter< Rcpp::List >::type points(pointsSEXP);
+    Rcpp::traits::input_parameter< bool >::type normalized(normalizedSEXP);
+    rcpp_result_gen = Rcpp::wrap(CPL_line_project(lines, points, normalized));
+    return rcpp_result_gen;
+END_RCPP
+}
+// CPL_line_interpolate
+Rcpp::List CPL_line_interpolate(Rcpp::List lines, Rcpp::NumericVector dists, bool normalized);
+RcppExport SEXP _sf_CPL_line_interpolate(SEXP linesSEXP, SEXP distsSEXP, SEXP normalizedSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< Rcpp::List >::type lines(linesSEXP);
+    Rcpp::traits::input_parameter< Rcpp::NumericVector >::type dists(distsSEXP);
+    Rcpp::traits::input_parameter< bool >::type normalized(normalizedSEXP);
+    rcpp_result_gen = Rcpp::wrap(CPL_line_interpolate(lines, dists, normalized));
+    return rcpp_result_gen;
+END_RCPP
+}
 // CPL_hex_to_raw
 Rcpp::List CPL_hex_to_raw(Rcpp::CharacterVector cx);
 RcppExport SEXP _sf_CPL_hex_to_raw(SEXP cxSEXP) {
@@ -1476,6 +1502,8 @@ static const R_CallMethodDef CallEntries[] = {
     {"_sf_CPL_transpose_sparse_incidence", (DL_FUNC) &_sf_CPL_transpose_sparse_incidence, 2},
     {"_sf_CPL_nary_difference", (DL_FUNC) &_sf_CPL_nary_difference, 1},
     {"_sf_CPL_nary_intersection", (DL_FUNC) &_sf_CPL_nary_intersection, 1},
+    {"_sf_CPL_line_project", (DL_FUNC) &_sf_CPL_line_project, 3},
+    {"_sf_CPL_line_interpolate", (DL_FUNC) &_sf_CPL_line_interpolate, 3},
     {"_sf_CPL_hex_to_raw", (DL_FUNC) &_sf_CPL_hex_to_raw, 1},
     {"_sf_CPL_raw_to_hex", (DL_FUNC) &_sf_CPL_raw_to_hex, 1},
     {"_sf_CPL_read_mdim", (DL_FUNC) &_sf_CPL_read_mdim, 8},

src/geos.cpp

@@ -1376,3 +1376,41 @@ Rcpp::List CPL_nary_intersection(Rcpp::List sfc) {
 	// return result
 	return ret;
 }
+
+// [[Rcpp::export]]
+Rcpp::NumericVector CPL_line_project(Rcpp::List lines, Rcpp::List points, bool normalized) {
+	GEOSContextHandle_t hGEOSCtxt = CPL_geos_init();
+	int dim = 2;
+	std::vector<GeomPtr> l = geometries_from_sfc(hGEOSCtxt, lines, &dim);
+	std::vector<GeomPtr> p = geometries_from_sfc(hGEOSCtxt, points, &dim);
+	Rcpp::NumericVector ret(p.size());
+	if (normalized) {
+		for (size_t i = 0; i < l.size() && i < p.size(); i++)
+			ret[i] = GEOSProjectNormalized_r(hGEOSCtxt, l[i].get(), p[i].get());
+	} else {
+		for (size_t i = 0; i < l.size() && i < p.size(); i++)
+			ret[i] = GEOSProject_r(hGEOSCtxt, l[i].get(), p[i].get());
+	}
+	CPL_geos_finish(hGEOSCtxt);
+	// return result
+	return ret;
+}
+
+// [[Rcpp::export]]
+Rcpp::List CPL_line_interpolate(Rcpp::List lines, Rcpp::NumericVector dists, bool normalized) {
+	GEOSContextHandle_t hGEOSCtxt = CPL_geos_init();
+	int dim = 2;
+	std::vector<GeomPtr> l = geometries_from_sfc(hGEOSCtxt, lines, &dim);
+	std::vector<GeomPtr> p(l.size());
+	if (normalized) {
+		for (int i = 0; i < (int) l.size() && i < dists.size(); i++)
+			p[i] = geos_ptr(GEOSInterpolateNormalized_r(hGEOSCtxt, l[i].get(), dists[i]), hGEOSCtxt);
+	} else {
+		for (int i = 0; i < (int) l.size() && i < dists.size(); i++)
+			p[i] = geos_ptr(GEOSInterpolate_r(hGEOSCtxt, l[i].get(), dists[i]), hGEOSCtxt);
+	}
+	Rcpp::List ret(sfc_from_geometry(hGEOSCtxt, p, dim));
+	CPL_geos_finish(hGEOSCtxt);
+	// return result
+	return ret;
+}