how do I pass a variable name to an argument in a function

Question

I am a new user to R and I want to recall a block of code for different variables and I want to do something like this:

   myfunc<- function(dat, groupvar, interestvar){
      a<- dat%>% group_by(groupvar) %>% summarize(m=mean(interestvar))
         ..... other codes ....
      return(a)   }

myfunc(data=newdata, groupvar=variable1, interestvar=variable3)
myfunc(data=newdata, groupvar=variable2, interestvar=varaible4)

Here the variable1-vari all are variables inside newdata. It seems if I call intrestvar=newdata$varaible3, that part will work. However, the way I call groupvar still don't tell the function the group by is done by variable1. How do I make it work?

Answer 1

You can use curly-curly operator ({{}}) from rlang to pass unquoted variable in the function.

library(dplyr)
library(rlang)

myfunc<- function(dat, groupvar, interestvar){
  a<- dat%>% group_by({{groupvar}}) %>% summarize(m=mean({{interestvar}}))
  return(a)   
}

myfunc(dat =mtcars, groupvar=cyl, interestvar=mpg)
#   cyl        m
#  <dbl>    <dbl>
#1     4 26.66364
#2     6 19.74286
#3     8 15.1    

myfunc(dat = mtcars, groupvar=am, interestvar=disp)
#     am        m
#  <dbl>    <dbl>
#1     0 290.3789
#2     1 143.5308