I want to rasterize categorical values from a shapefile of points to a raster. I used to be able to do this, but my code is no longer working.
Here's a reproducible example:
points <- tibble::tribble(
~x,~y, ~cat,
-34.125, -58.162,'a',
-34.225, -58.462,'b',
-34.325, -58.362,'c',
-34.425, -58.662,'d',
-34.525, -58.762,'e',
-34.625, -58.862,'f'
)
points <- st_as_sf(points, coords = c("x", "y"), crs = 4326)
polygons <- st_buffer(points, dist = 0.1)
v1 <- vect(points)
v2 <- vect(polygons)
r <- rast(v1, res=0.1)
rasterize(v1, r, 'cat')
rasterize(v2, r, 'cat')
As a result, I get:
class : SpatRaster
dimensions : 7, 5, 1 (nrow, ncol, nlyr)
resolution : 0.1, 0.1 (x, y)
extent : -34.625, -34.125, -58.862, -58.162 (xmin, xmax, ymin, ymax)
coord. ref. : lon/lat WGS 84 (EPSG:4326)
source(s) : memory
name : cat
min value : 0
max value : 5
and
class : SpatRaster
dimensions : 7, 5, 1 (nrow, ncol, nlyr)
resolution : 0.1, 0.1 (x, y)
extent : -34.625, -34.125, -58.862, -58.162 (xmin, xmax, ymin, ymax)
coord. ref. : lon/lat WGS 84 (EPSG:4326)
source(s) : memory
categories : cat
name : cat
min value : a
max value : e
So, it works for polygons but not for points.
I want that the char value is returned, not the numeric value.
Also, I used to be able to use first as a function, but this seems no longer supported.
Thanks!
You can set the levels after rasterizing:
p <- data.frame(
x = c(-34.125, -34.225, -34.325, -34.425, -34.525, -34.625),
y = c(-58.162, -58.462, -58.362, -58.662, -58.762, -58.862),
cat = factor(c("a", "b", "c", "d", "e", "f")))
library(terra)
#terra 1.7.78
v <- vect(p, c("x", "y"), crs = "epsg:4326")
r <- rast(v, res=0.1)
x <- rasterize(v, r, 'cat')
levels(x) <- data.frame(id=0:5, cat=levels(p$cat))
x
#class : SpatRaster
#dimensions : 7, 5, 1 (nrow, ncol, nlyr)
#resolution : 0.1, 0.1 (x, y)
#extent : -34.625, -34.125, -58.862, -58.162 (xmin, xmax, ymin, ymax)
#coord. ref. : lon/lat WGS 84 (EPSG:4326)
#source(s) : memory
#categories : cat
#name : cat
#min value : a
#max value : f