r1 <- raster(nrow=10, ncol=10)
r1 <- setValues(r1, runif(ncell(r1)))
r2 <- setValues(r1, runif(ncell(r1)))
r3 <- setValues(r1, runif(ncell(r1)))
r <- max(r1, r2, r3)
r <- range(r1, r2, r3, 1.2)
s <- stack(r1, r2, r3)
r <- mean(s, 2)
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