CODEWITHSUNDEEP
rdplyrtidyverse
Parseltongue
Parseltongue

Reputation: 11707

Mutate a data frame in the tidyverse passed as a parameter in a function

I'm trying to create a function where you can pass a data frame and the name of one of the columns. Within the function it should mutate the data frame to create a scaled version of the column you sent. Here's my attempt:

test_scale <- function(outcome, data){
  outcome_scaled = paste0(outcome, "_s")
  data = data %>% mutate(!!outcome_scaled := scale(as.numeric(outcome)))
  print(head(data[, outcome_scaled]))
}

However, this doesn't work since it just prints the text of whatever outcome I pass it.

> test_scale("age", df)
mutate: new variable 'age_s' (character) with one unique value and 0% NA
[1] "age" "age" "age" "age" "age" "age"

How do I get the actual value of outcome instead of the string text of the outcome variable that's passed?

Upvotes: 2

Views: 338

Answers (1)

jared_mamrot
jared_mamrot

Reputation: 26225

Edit

Ritchie Sacramento's answer in the comments is better; use that.

--

Here is one potential solution:

library(tidyverse)

test_scale <- function(outcome, data){
  outcome <- ensym(outcome)
  outcome_scaled = paste0(outcome, "_s")
  data2 = data %>% mutate(outcome_scaled := scale(as.numeric(!!outcome)))
  print(head(data2[, "outcome_scaled"]))
}
test_scale("Sepal.Length", iris)
#>            [,1]
#> [1,] -0.8976739
#> [2,] -1.1392005
#> [3,] -1.3807271
#> [4,] -1.5014904
#> [5,] -1.0184372
#> [6,] -0.5353840

Using ensym() means that you don't necessarily need to quote "outcome":

test_scale(Sepal.Length, iris)
#>            [,1]
#> [1,] -0.8976739
#> [2,] -1.1392005
#> [3,] -1.3807271
#> [4,] -1.5014904
#> [5,] -1.0184372
#> [6,] -0.5353840

Created on 2021-12-02 by the reprex package (v2.0.1)

Upvotes: 1

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