R - Function to combine index from vector and raster stack layers

Question

I am trying to write an efficient script to calibrate hundreds of Landsat 8 images. At a certain point of the calibration steps, I need to apply some coefficients in each layer of a raster stack.

This is one sample stack:

fn <- system.file("external/test.grd", package="raster")
s  <- stack(fn, fn)

And these are sample coefficients:

mult <- c(0.0003342, 0.0005534) 
add  <- c(0.1, 0.2) 

What I need to is to apply each index of the coefficients to the correspondent index of the stack layer, like in this example:

s[[1]] <- (s[[1]] * mult[1]) + add[1]
s[[2]] <- (s[[2]] * mult[2]) + add[2]

This is my poor attempt, which obviously does not work:

cal.fun <- function(x) { 
x <- (x * mult) + add 
}

s.cal <- calc(s, cal.fun, progress='text')

Any ideas on how to do that?

Many thanks.

Answer 1

raster is a phenomenally well-constructed package and you can simply do:

s2 <- s * mult + add

For quick visual confirmation that that vectorized call "just works", do something like this:

library(gridExtra)
library(rasterVis)
grid.arrange(levelplot(s), levelplot(s2), nrow=2)