rowwise

I'm trying to return a list using mutate and rowwise but get the error shown in the code. These questions Q1 Q2 helped, but I'd like to keep it simple by iterating over rows using rowwise() , and the questions are 3yr 7mth old. Thanks. library(tidyverse) df <- data.frame(Name=c("a","a","b","b","c"),X=c(1,2,3,4,5), Y=c(2,3,4,2,2)) TestFn <- function(X,Y){ Z <- list(X*5,Y/2,X+Y,X*2+5*Y) return (Z) } #this works SingleResult <- TestFn(5,20) #error - Error in mutate_impl(.data, dots) : incompatible size (4), expecting 1 (the group size) or 1 dfResult <- df %>% rowwise() %>% mutate(R=TestFn(X,Y))