Element-wise mean in R

A tidyverse solution usign purrr:

library(purrr)
a <- c(1, 2, 3, 4)
b <- c(NA, 6, 7, 8)

# expected:
c(1, 4, 5, 6) 
#> [1] 1 4 5 6

# actual:
map2_dbl(a,b, ~mean(c(.x,.y), na.rm=T)) # actual
#> [1] 1 4 5 6

And for any number of vectors:

>  pmap_dbl(list(a,b, a, b), compose(partial(mean, na.rm = T), c))
 [1] 1 4 5 6

I'm not exactly sure what you are asking for, but does

apply(rbind(a,b),2,mean,na.rm = TRUE)

do what you want?

how about:

rowMeans(cbind(a, b), na.rm=TRUE)

or

colMeans(rbind(a, b), na.rm=TRUE)