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I'm working with a raster stack of 300 SGS, sims, and a raster layer, trend. I'm trying to sum trend to each of the raster layers in the stack. My end goal is to have a new raster stack of my simulations with the trend map so that I can then preform other operations.

what i was looking for would be something like:

sims1 <- sims + trend

so that each layer would be somewhat like this:

>names(sims1)
[1] "sim1+trend" "sim2+trend" "sim3+trend" "sim4+trend"...
noob_researcher
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2 Answers2

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list_sims <- list() # list to save sums 
for (i in 1:nlayers(sims)) { 
       list_sims[[i]] <- sims[[i]] + trend 
}
sims1 <- stack(list_sims)
Robert Hijmans
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noob_researcher
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Operations in R are typically vectorized with recycling of the short variables. Thus you can do

1:3 + 10
#[1] 11 12 13

The same applies to raster data.

Example data:

library(raster)
sims <- stack(system.file("external/rlogo.grd", package="raster")) 
trend <- raster(sims)
values(trend) <- 1:ncell(trend)

Solution:

x <- sims + trend
names(x) <- paste0(names(sims), ".trend")

x
#class      : RasterBrick 
#dimensions : 77, 101, 7777, 3  (nrow, ncol, ncell, nlayers)
#resolution : 1, 1  (x, y)
#extent     : 0, 101, 0, 77  (xmin, xmax, ymin, ymax)
#crs        : +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
#source     : memory
#names      : red.trend, green.trend, blue.trend 
#min values :       256,         256,        256 
#max values :      8032,        8032,       8032
Robert Hijmans
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