RWmisc (version 0.1.2)

overlap.weight: Weight Raster Cells by Overlapping Polygons

Description

Weight raster cells by overlapping polygons to avoid over-counting when aggregating by polygons

Usage

overlap.weight(raster, polygons, count = FALSE, warn = TRUE)

Arguments

raster

a RasterLayer object.

polygons

a SpatialPolygons, SpatialPolygonsDataFrame, or simple feature collection with at least two features. The function will still work with only one polygon, but values will be unchanged, and the result will be equivalent to mask(raster, polygons).

count

a logical indicating whether to return a raster with the count of polygons intersecting each cell, or a raster with original values weighted by 1/number of intersecting polygons.

warn

include warnings? Most common is that the returned raster will be an intersection of the raster and the polygons. Default TRUE.

Value

a RasterLayer object.

Details

This function takes a raster and a set of polygons as arguments. It counts the number of polygons that intersect each raster cell. It can return either a raster with the count of the number of intersecting polygons as cell values or the original raster with cell values weighted by 1 / the number of intersecting polygons (the default behavior). Cells that do not intersect any polygons will receive a value of NA. If the extent of the polygons is less than the extent of the raster, then the function will warn that it is cropping the raster to the polygons' extent.

Examples

# NOT RUN {
library(sf)
library(raster)
polys_t <- st_sfc(list(st_polygon(list(rbind(c(2,2), c(2,6),
                                             c(6,6), c(6,2),
                                             c(2, 2)))),
                       st_polygon(list(rbind(c(8,8), c(4,8),
                                             c(4,4), c(8,4),
                                             c(8,8))))),
                  crs = st_crs('OGC:CRS84'))
raster_t <- raster(nrows = 10, ncols = 10, xmn = 0,
                   xmx = 10, ymn = 0, ymx = 10,
                   vals = 1:100,
                   crs = CRS(st_crs(polys_t)$proj4string))
overlap.weight(raster_t, polys_t)
# }