ggplot2plotrasterterravisualisation
If I have a spatraster with 6 layers, rasterVis::levelplot will give a 2 rows and 3 columns plot.
How can I change it to 3 rows and 2columns?
library(rasterVis)
library(terra)
f <- system.file("external/test.grd", package="raster")
rt1 <- rast(f)
rt2 <- rast(f)
rt3 <- rast(f)
rt4 <- rast(f)
rt5 <- rast(f)
rt6 <- rast(f)
rt <- c(rt1,rt2,rt3,rt4,rt5,rt6)
names(rt) <- LETTERS[1:6]
levelplot(rt)
The raster package fails for me with that data:
> r = raster(f)
proj_create: Error -22: lat_0, lat_1 or lat_2 >= 90
proj_create: Error -22: lat_0, lat_1 or lat_2 >= 90
Error in .rasterObjectFromFile(x, band = band, objecttype = "RasterLayer", :
Cannot create a RasterLayer object from this file.
Oh well. terra works:
> r = rast(f)
> r
class : SpatRaster
dimensions : 8827, 10224, 1 (nrow, ncol, nlyr)
resolution : 1000, 1000 (x, y)
extent : -5762000, 4462000, -3920000, 4907000 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=laea +lat_0=-100 +lon_0=6370997 +x_0=45 +y_0=0 +datum=WGS84 +units=m +no_defs
source : w001001.adf
name : VALUE
min value : -76
max value : 5930
The problem appears to be due to terra thinking this is a categorical raster, with levels. That's why the plot appears differently. Also:
> is.factor(r)
[1] TRUE
which shouldn't be true for a numeric raster:
> is.factor(rast(matrix(1:12,3,4)))
[1] FALSE
but is for one made of letters:
> is.factor(rast(matrix(letters[1:12],3,4)))
[1] TRUE
I can't find any documentation on how to make rast read in as numeric, or how to convert from one to the other (as.numeric doesn't work) but adding "0" seems to work:
plot(r+0)
There may be documentation somewhere or this may be changed in a later release, I guess.
[ask your second Q in a separate post]
You can simply index the rasters. In this example we will subset the (1, 3-4, 10) rasters. Note the double brackets.
library(terra)
x <- rast(nlyrs = 10, nrows=108, ncols=21, xmin=0, xmax=10)
y <- x[[c(1, 3:4, 10)]]
For your needs you can use
y1 <- x[[1:5]]
y2 <- x[[6:10]]
Unlike the raster package, to add a raster you can simply use concatenate.
y <- c(y, x[[2]])
There are also some formal methods in terra, see; subset, selectRange and, add
Best Answer
You can do