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rconditional-statementsstackraster

Conditional selection of values from 2 raster stack

I am working with 2 raster::stack (RS1 and RS2) of 2 equal time series. I need to create a third raster (RS3) which is the result of the pixel by pixel criterion -> if: RS1 > RS2 then RS1, else RS2.

I tried with ifelse unsuccessfully:

RS3 <-ifelse(RS1[] > RS2[], RS1[], RS2[])

I don't know how to go from here.

Solution

  • Example data and using "terra" instead of the (obsolete) "raster" package.

    library(terra)
r <- rast(system.file("ex/elev.tif", package="terra"))
x <- c(r, r/2, r*2)
y <- c(r/2, r*2, r)

    Solution:

    z <- max(x, y)

    min and max values:

    minmax(x)
#    elevation elevation elevation
#min       141      70.5       282
#max       547     273.5      1094
minmax(y)
#    elevation elevation elevation
#min      70.5       282       141
#max     273.5      1094       547
minmax(z)
#    elevation elevation elevation
#min       141       282       282
#max       547      1094      1094

    For more complex functions than max, that are not "built-in", you can use lapp like this

    zz <- lapp(sds(x, y), pmax)