R: How to combine rasters in a loop with all possible combinations?

Question

I have three raster in a list .

rasterlist <- (r1, r2, r3)

I have one operation to combine each raster with another - let's say add them.

How do I write a loop which combines all the rasters iteratively?

Like this:

result1 <- r1+r2 
result2 <- r2+r3
result3 <- r1+r3

Note: My operation within {} is around 200 lines long and not a simple addition, which is why I need a nice loop around.

Answer 1

我们可以使用combn来获取list元素的组合并求和

combn(rasterlist, 2, FUN = function(x) x[1] + x[2])