Average of list of unequal length in R

Question

I have list of vectors of unequal lengths. What I want is the avg. at each index. For example:

a = c(2,3,4)
b = c(2,3,4,5) 
c = c(5,0,3,4,6)

avg(a,b,c) = c(9/3, 6/3, 11/3, 9/2, 6/1)

How to achieve this in R ?

Answer 1

We can place the vectors in a list , pad NA for list elements that have less number of element and do the rowMeans

lst <- list(a, b, c)
rowMeans(sapply(lst, `length<-`, max(lengths(lst))), na.rm=TRUE)
#[1] 3.000000 2.000000 3.666667 4.500000 6.000000

data

a <- 2:4
b <- 2:5
c <- c(5, 0, 3, 4, 6)

Answer 2

You can use cbind.fill function in rowr package

cbind the data with fill option as NA and apply colMeans on the t ranspose of the data.frame

library(rowr)
colMeans(t(cbind.fill(a, b, c, fill = NA)), na.rm = T)

#[1] 3.000000 2.000000 3.666667 4.500000 6.000000

Answer 3

How about this using base R:

ls <- list(a, b, c)
sapply(1:max(lengths(ls)), function(i) mean(sapply(ls, function(x) x[i]), na.rm = T))

# [1] 3.000000 2.000000 3.666667 4.500000 6.000000

The idea is to apply the mean function on ls (on the 1th, 2th, 3th, ... of each vector in list) and ignoring NA values.