I have a raster whose extent is -180.049996946546, 179.949996948242, -90.05, 90.05 (xmin, xmax, ymin, ymax). I need it to allign it with other rasters that have the same CRS but an extent of -180, 180, -90, 90 (xmin, xmax, ymin, ymax). I am trying to cut it using the crop function of the terra package but for some reasons this does not return the exact extent I want, namely -180, 180, -90, 90 (xmin, xmax, ymin, ymax).
Can anyone advice?
myraster |> ext()
SpatExtent : -180.049996946546, 179.949996948242, -90.05, 90.05 (xmin, xmax, ymin, ymax)
new_extent
SpatExtent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
myraster_cropped=crop(myraster,new_extent ,extend=TRUE)
myraster_cropped |> ext()
SpatExtent : -180.049996946546, 180.049996946546, -89.95, 90.05 (xmin, xmax, ymin, ymax)
Details of myraster
> myraster
class : SpatRaster
dimensions : 1801, 3600, 1 (nrow, ncol, nlyr)
resolution : 0.1, 0.1 (x, y)
extent : -180.05, 179.95, -90.05, 90.05 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84 +no_defs
source(s) : memory
varname : t2m (2 metre temperature)
name : t2m_1
min value : 229.8191
max value : 306.1671
unit : K
time : 2000-01-01 UTC
Your data
libary (terra)
r <- rast(xmin=-180.05, xmax=179.95, ymin=-90.05, ymax=90.05, res=.1)
This is, of course, a very odd extent. Especially having latitudes >90 and < -90 makes no sense. Unfortunately, climate model data if often provided that way.
If you do
newext <- ext(-180, 180, -90, 90)
crop(r, newext) |> ext()
#SpatExtent : -180.05, 179.95, -89.95, 89.95 (xmin, xmax, ymin, ymax)
The extent does not change the way you would like because crop can only remove entire rows and columns. You can use terra::resample
x <- rast(res=0.1)
x <- resample(r, x)
And, yes this will change the values (depending on the value for argument "method") but that is desirable in this case since the extent shifts half a cell, there is no good way around that.