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I'm hoping to produce a pipe-friendly function where a user specifies the "name of choice" for a new column produced by the function as one of the function arguments.

In the function below, I'd like name_for_elective to be something that the user can set at will, and afterwards, the user could expect that there will be a new column in their data with the name that they provided here.

I've looked at https://dplyr.tidyverse.org/reference/dplyr_data_masking.html, the mutate() function documentation, searched here, and tried working with https://dplyr.tidyverse.org/reference/rename.html, but to no avail.

 elective_open<-function(.data,name_for_elective,course,tiebreaker){ 
    name_for_elective<-rlang::ensym(name_for_elective)
    course<-rlang::ensym(course)
    tiebreaker<-rlang::ensym(tiebreaker)

     .data%>%
       mutate(!!name_for_elective =ifelse(!!tiebreaker==max(!!tiebreaker),1,0))%>%mutate(!!name_for_elective=ifelse(!!name_for_elective==0,!!course[!!name_for_elective==1],""))%>%
   filter(!(!!course %in% !!name_for_elective))

 }

I've included this example function because there are several references to the desired new column name, and I'm unsure if the context in which the reference is made changes syntax.

As you can see, I was hoping !!name_for_elective would let me name our new column, but no. I've played with {{}}, not using rlang::ensym, and still haven't got this figured out.

Any solution would be greatly appreciated.

This: Use dynamic variable names in `dplyr` may be helpful, but I can't seem to figure out how to extend this to work in the case where multiple references are made to the name argument.

Example data, per a good suggestion by @MrFlick, takes the form below:

dat<-tibble(ID=c("AA","BB","AA","BB","AA","BB"),Class=c("A_Class","B_Class","C_Class","D_Class","E_Class","F_Class"),
        randomNo=c(.75,.43,.97,.41,.27,.38))

The user could then run something like:

dat2<-dat%>%
   elective_open(MyChosenName,Class,randomNo)

A desired result, if using the function a single time, would be:

desired_result_1<-tibble(ID=c("AA","BB","AA","BB"),
                   Class=c("A_Class","D_Class","E_Class","F_Class"),
                   randomNo=c(.75,.41,.27,.38),
                   MyChosenName=c("C_Class","B_Class"))

The goal would be to allow this function to be used again if so desired, with a different name specified.

In the case where a user runs:

dat3<-dat%>%
   elective_open(MyChosenName,Class,randomNo)%>%
   mutate(Just_Another_One=1)%>%
   elective_open(SecondName,Class,randomNo)

The output would be:

desired_result_2<-tibble(ID=c("AA","BB"),
                     Class=c("E_Class","F_Class"),
                     randomNo=c(.27,.38),
                     MyChosenName=c("C_Class","B_Class"),
                     Just_Another_One=c(1,1),
                     SecondName=c("A_Class","D_Class"))

In reality, there may be any number of records with the same ID, and any number of Class-es.

Pake
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1 Answers1

3

In this case you can just stick to using the embrace {{}} option for your variables. If you want to dynamically create column names, you're going to still need to use :=. The difference here is that you can use the glue-style syntax with the embrace operator to get the name of the symbol. This works with the data provided.

elective_open <- function(.data, name_for_elective, course, tiebreaker){ 
  .data%>%
    mutate("{{name_for_elective}}" := ifelse({{tiebreaker}}==max({{tiebreaker}}),1,0)) %>%
    mutate("{{name_for_elective}}" := ifelse({{name_for_elective}}==0,{{course}}[{{name_for_elective}}==1],"")) %>%
    filter(!({{course}} %in% {{name_for_elective}}))
}
MrFlick
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