Define a new variable name based on a conditon within R dplyr universe (mutate, if, ifelse)

Question

I want to add a new variable in an dplyr workflow and define the variable name based on a condition. There is a lot of discussion on conditional mutating with ifelse() out there on how to define values of a given variable, but not on how to conditionally define the name.

Something like:

Test <- 'A'
Test_results <- c(1.1, 33, 343, 2.22, 2.4)
##
iris<- iris%>%
 dplyr::mutate(
  ifelse(Test=='A',
         Test_A=Test_results,
         ifelse(Test=='B',
                Test_B=Test_results,
                no_Test='no_results')) )

Desired output (given that Test <- 'A') is:

> iris
    Sepal.Length Sepal.Width Petal.Length Petal.Width    Species  Test_A
1            5.1         3.5          1.4         0.2     setosa     1.1
2            4.9         3.0          1.4         0.2     setosa      33
3            4.7         3.2          1.3         0.2     setosa     343
4            4.6         3.1          1.5         0.2     setosa    2.22
5            5.0         3.6          1.4         0.2     setosa     2.4
...

If Test <- 'B' the result should be:

 > iris
        Sepal.Length Sepal.Width Petal.Length Petal.Width    Species  Test_B
    1            5.1         3.5          1.4         0.2     setosa     1.1
    2            4.9         3.0          1.4         0.2     setosa      33
    3            4.7         3.2          1.3         0.2     setosa     343
    4            4.6         3.1          1.5         0.2     setosa    2.22
    5            5.0         3.6          1.4         0.2     setosa     2.4
...

The variable "Test" is defined somewhere in the users cockpit and does effects on multiple nested scripts (so no hard coding pls).

Answer 1

dplyr::rename_at should work. Create a column with the tests and rename it with a function that depends on Test.

Test <- 'A'
Test_results <- c(1.1, 33, 343, 2.22, 2.4)

iris %>%
  head(n = 5) %>%
  mutate(Test_results = Test_results) %>%
  rename_at('Test_results', \(x) case_when(Test %in% c('A', 'B') ~ paste0('Test_', Test),
                                           TRUE ~ 'no_results'))