in the frame of soil mapping, I need to sum a undetermined number of rasters. I try to do it using the 'raster' package and the 'do.call' function. However, if the 'sum' function can sum up to many rasters, doing the same operation using do.call leads to an error. What am I doing wrong ?
library(raster)
r1 <- raster(ncol=10, nrow=10) # dataset for test
values(r1) <- runif(ncell(r1))
r2 <- raster(ncol=10, nrow=10)
values(r2) <- runif(ncell(r2))
r3 <- raster(ncol=10, nrow=10)
values(r3) <- runif(ncell(r3))
sum(r1,r2,r3) # works nice
do.call(sum,list(r1,r2,r3))
##Erreur dans as.character(sys.call()[[1L]]) :
##cannot coerce type 'builtin' to vector of type 'character'
Thank you for you help,
François
You could use Reduce and + to compute the sum from a list:
Reduce("+",list(r1,r2,r3))
class : RasterLayer
dimensions : 10, 10, 100 (nrow, ncol, ncell)
resolution : 36, 18 (x, y)
extent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84
data source : in memory
names : layer
values : 0.4278222, 2.476625 (min, max)
As for why your original command doesn't work, that is somewhat perplexing. Supplying the function name as a character seems to work:
do.call("sum",list(r1,r2,r3))
class : RasterLayer
dimensions : 10, 10, 100 (nrow, ncol, ncell)
resolution : 36, 18 (x, y)
extent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=WGS84
data source : in memory
names : layer
values : 0.4278222, 2.476625 (min, max)
But this isn't required in other contexts:
do.call(sum,list(1,2,3))
[1] 6