Raster extent issue in R

Question

So, I have two different rasters, and I am trying to match their extent, even though the difference in their existing extents is quite small, but still raster::stack won't stack which is understandable. But, when I use the crop function to crop one raster on the basis of the other raster's extent, their extents still don't match up i.e., xmax of rast1 doesn't change from 757322.8 to 757322.7. . How can I solve this problem, when the purpose of stacking them together to compute standard deviation? I also tried using the raster::extend function but that is giving me a memory error.

library(raster)  
rast1 = raster::brick("path/rast1.tif")

rast2 = raster::brick("path/rast2.tif")

# Get the extent 
extent(rast1)

class      : Extent 
xmin       : 756472.2 
xmax       : 757322.8 
ymin       : 4074670 
ymax       : 4074953 

extent(rast2)

class      : Extent 
xmin       : 756472.2 
xmax       : 757322.7 
ymin       : 4074670 
ymax       : 4074953 

extent_1 = c(756472.2 ,4074670 ,757322.7 ,4074953)
rast1_Crop = crop(rast1, extent_1)
stack = raster::stack(rast1_Crop , rast_2)

Error

Error in compareRaster(x) : different extent

Answer 1

crop can only cut entire cells (rows, columns) so that won't help you here.

If you want to ignore the small difference, and the rasters have the same number of rows and columns, you can do

library(raster)
r1 = raster::brick("path/rast1.tif")
r2 = raster::brick("path/rast2.tif")
extent(r2) <- extent(r1)
s <- stack(r1, r2)

That is not generally a good idea; but given the very small difference it would seem OK here. And it is very efficient.

More generally, you can resample one raster to the structure of another like this

library(raster)
r1 = raster::brick("path/rast1.tif")
r2 = raster::brick("path/rast2.tif")
r1 <- resample(r1, r2)
s <- stack(r1, r2)

For better speed with resample, use terra instead

library(terra)
r1 = rast("path/rast1.tif")
r2 = rast("path/rast2.tif")
r1 <- resample(r1, r2)
s <- c(r1, r2)

And likewise you could do

r1 = rast("path/rast1.tif")
r2 = rast("path/rast2.tif")
ext(r1) <- ext(r2)
s <- c(r1, r2)