How to make long argument in function reflected in R

Question

Thanks for all your helps.

I want to make macro with function with R. In function , there is long argument. This argument will not print or return specific value. But I want to make the results of arguments be reflected.

For example, I made some arguments with dplyr

The i will be dataframe. I created the dataset test

set.seed(1001)
a<-rnorm(10)
b<-rnorm(10)
test<-data.frame(cbind(a,b))
test

Then I want to make column c . The c will be a minus b

fun<-function(i){
i<-i%>%mutate(c=a-b)}
fun(i=test)

But, when i checked the test , the c variable was not generated.

How to make the results of arguments in function reflected?

Answer 1

You need to add return in the function and assign the value back to test . Or since R by default returns the last line of the function, you can do

library(dplyr)

fun <- function(i) i %>% mutate(c = a - b)
test <- fun(test)
test

#        a      b      c
#1   2.189  0.303  1.886
#2  -0.178  1.634 -1.812
#3  -0.185 -0.622  0.437
#4  -2.507  0.467 -2.974
#5  -0.557  1.419 -1.977
#6  -0.144  0.110 -0.254
#7   1.092  1.870 -0.778
#8  -0.623 -1.030  0.407
#9  -0.907 -1.342  0.434
#10 -1.594  0.554 -2.148