rsaga.intersect.polygons: Spatial intersection of two polygon layers
In debangs/RSAGA: SAGA Geoprocessing and Terrain Analysis in R

Description Usage Arguments Details Value Author(s) Examples

The function rsaga.intersect.polygons calculates the geometric intersection of two overlayed polygon layers using SAGA module "Intersect".

1 2	rsaga.intersect.polygons(layer_a = NULL, layer_b = NULL, result = NULL, split = FALSE, load = FALSE, env = rsaga.env())

`layer_a`	A `character`-string representing the path to a polygon shapefile or a spatial object of class `SpatialPolygonsDataFrame`.
`layer_b`	A `character`-string representing the path to a polygon shapefile or a spatial object of class `SpatialPolygonsDataFrame` with which to intersect layer_a.
`result`	A `character`-string indicating where the resulting shapefile should be stored.
`split`	If `TRUE`, multipart polygons become separated polygons (default: FALSE).
`load`	If `TRUE`, the resulting output shapefile will be loaded into R (default: FALSE).
`env`	RSAGA geoprocessing environment created by `rsaga.env`, required because module(s) depend(s) on SAGA version.

Function gIntersection can also be used to define the intersection between two polygon layers. However, rsaga.intersect.polygons will be usually much faster, especially when intersecting thousands of polygons.

The function saves the output shapefile to the path indicated in function argument result and loads the resulting shapefile into R when function parameter load is set to TRUE.

Jannes Muenchow (R interface), Olaf Conrad and Angus Johnson (SAGA modules)

library("RSAGA")
library("sp")
library("magrittr")
# construct coordinates of two squares
coords_1 <- matrix(data = c(0, 0, 1, 0, 1, 1, 0, 1, 0, 0),
                 ncol = 2, byrow = TRUE)
coords_2 <- matrix(data = c(-0.5, -0.5, 0.5, -0.5, 0.5, 0.5, -0.5, 0.5, 
                            -0.5, -0.5),
                 ncol = 2, byrow = TRUE)
# convert the coordinates into polygons
poly_1 <- SpatialPolygons(list(Polygons(list(Polygon(coords_1)), 1))) %>%
  as(., "SpatialPolygonsDataFrame")
poly_2 <- SpatialPolygons(list(Polygons(list(Polygon(coords_2)), 1))) %>%
  as(., "SpatialPolygonsDataFrame")
# intersect the two polygons using SAGA and load the output
dir_tmp <- paste0(tempdir(), "/out.shp")
res <- rsaga.intersect.polygons(layer_a = poly_1,
                                layer_b = poly_2,
                                result = dir_tmp,
                                load = TRUE)
# plot input polygons
plot(poly_1, col = "red", axes = TRUE, xlim = c(-1, 1), ylim = c(-1, 1))
plot(poly_2, col = "blue", add = TRUE)
# plot the intersection
plot(res, col = "yellow", add = TRUE)