Count Points within Polygons by Species
Source:R/count_points_in_polygons.R
count_points_in_polygons.RdCounts the number of points per species within each polygon. If the points dataset contains a `species` column, a separate column is created for each species with the counts inside each polygon. Spaces in species names are replaced with underscores for naming columns.
This function is particularly useful in ecological studies where species have different spatial distributions. It accounts for the possibility that some species may not be present in all polygons, producing zero counts in those cases.
Value
An `sf` object containing the original polygons and additional columns for each species count. Column names follow the format `species_name_count`, with spaces replaced by underscores.
Details
The function performs a spatial join to count occurrences of each species within each polygon. For species absent in a polygon, the count will be zero. This approach allows for flexible analysis of species distributions across landscape units.
Examples
# \donttest{
library(sf)
#> Linking to GEOS 3.12.1, GDAL 3.8.4, PROJ 9.4.0; sf_use_s2() is TRUE
points_sf <- st_as_sf(data.frame(
id = 1:6,
species = c("Panthera onca", "Panthera onca", "Felis catus",
"Felis catus", "Felis catus", "Panthera leo"),
x = c(1, 2, 3, 4, 5, 6),
y = c(1, 2, 3, 4, 5, 6)
), coords = c("x", "y"), crs = 4326)
polygons_sf <- st_as_sf(data.frame(
id = 1:2,
geometry = st_sfc(
st_polygon(list(rbind(c(0,0), c(3,0), c(3,3), c(0,3), c(0,0)))),
st_polygon(list(rbind(c(3,3), c(6,3), c(6,6), c(3,6), c(3,3))))
)
), crs = 4326)
result <- count_points_in_polygons(points_sf, polygons_sf)
print(result)
#> Simple feature collection with 2 features and 4 fields
#> Geometry type: POLYGON
#> Dimension: XY
#> Bounding box: xmin: 0 ymin: 0 xmax: 6 ymax: 6
#> Geodetic CRS: WGS 84
#> id geometry Panthera_onca Felis_catus Panthera_leo
#> 1 1 POLYGON ((0 0, 3 0, 3 3, 0 ... 2 1 0
#> 2 2 POLYGON ((3 3, 6 3, 6 6, 3 ... 0 3 1
# }