I have a DEM raster file of a specific region
DEMRASTER
class : RasterLayer
dimensions : 47, 89, 4183 (nrow, ncol, ncell)
resolution : 0.5, 0.5 (x, y)
extent : 60.75, 105.25, 15.75, 39.25 (xmin, xmax, ymin, ymax)
crs : NA
source : memory
names : newlowelevation1
values : 1, 6136.012 (min, max)
I have another raster file of variable "GPP":
GPPRASTER
class : RasterLayer
dimensions : 47, 89, 4183 (nrow, ncol, ncell)
resolution : 0.5, 0.5 (x, y)
extent : 60.75, 105.25, 15.75, 39.25 (xmin, xmax, ymin, ymax)
crs : NA
source : memory
names : layer
values : -0.333333, 0 (min, max)
How can I find the values of the GPP raster according to elevation? For instance, if I want to find a mean value of GPP for elevation from 0-2000m or 5500 to 6136m? What will be the basic code for this?
I have tried removing pixels based on the elevation that I did not want from the DEM raster file, but it is a method that takes too long. I am sure that there is a code for this, but can't put my hand on it as I am a new beginner at R myself. Thanks in advance!
Here is a minimal self-contained, reproducible example:
library(raster)
elev <- raster(ncol=47, nrow=89, ext=extent(60.75, 105.25, 15.75, 39.25))
elev <- init(elev, "cell")
gdp <- flip(elev, "y")/100
Solution:
ezones <- cut(elev, c(0,1000,2000,Inf))
zonal(gdp, ezones)
# zone mean
#[1,] 1 36.83058
#[2,] 2 26.83396
#[3,] 3 10.92250
Or with terra:
library(terra)
#terra version 1.2.1
ev <- rast(ncol=47, nrow=89, ext=ext(60.75, 105.25, 15.75, 39.25))
ev <- init(ev, "cell")
gd <- flip(ev, "vertical")/100
names(gd) <- "gdp"
names(ev) <- "elevation"
Solution:
ez <- classify(ev, c(0,1000,2000,Inf))
zonal(gd, ez)
# elevation gdp
#1 0 - 1000 36.83580
#2 1000 - 2000 26.84370
#3 2000 - inf 10.92752