[R] function problem: multi selection in one argument

[Rui Barradas]

Hello,

Here are 3 functions that do what the question asks for. The first 2 are 
tidyverse solutions, the last one a base R function.

I don't understand why the group_by and mutate, that's why I've included 
a 2nd tidyverse function. And the base R function follows the same lines 
of outputing the table only without data transformation.

And the test dataset is not iris, it only has one factor variable. It 
doesn't make sense to table a continuous variable such as Petal.Width.

The data set mtcars has several numeric variables that are in fact 
categorical ("vs", "am") and one, "cyl", that can be tabled. The 
examples below use mtcars.



f3 <- function(data, ...){
   groups <- unlist(list(...))
   temp <- data %>%
     select(all_of({{groups}})) %>%
     group_by(across(all_of({{groups}}))) %>%
     mutate(numbering = row_number(), max = n())
   temp %>%
     select(all_of({{groups}})) %>%
     table()
}

f4 <- function(data, ...){
   groups <- unlist(list(...))
   data %>%
     select(all_of({{groups}})) %>%
     table()
}

f5 <- function(data, ...){
   temp <- lapply(list(...), \(col) data[[col]])
   table(setNames(temp, list(...)))
}

f3(mtcars, "am", "cyl")
f4(mtcars, "am", "cyl")
f5(mtcars, "am", "cyl")


Hope this helps,

Rui Barradas

Às 00:14 de 25/01/2022, Kai Yang via R-help escreveu:
> Hello Team,
> I can run the function below:
>
> library(tidyverse)
>
> f2 <- function(indata, subgrp1){
>    indata0 <- indata
>    temp    <- indata0 %>% select({{subgrp1}}) %>% arrange({{subgrp1}}) %>%
>      group_by({{subgrp1}}) %>%
>      mutate(numbering =row_number(), max=max(numbering))
>    view(temp)
>    f_table <- table(temp$Species)
>    view(f_table)
>    return(f_table)
> }
> f2(iris, Species)
>
> You can see the second argument I use Species only, and it works fine.
> But If I say, I want the 2nd argument = Petal.Width, Species , how should I write the argument? I did try f2(iris, c(Petal.Width, Species)), but I got error message:
> Error: arrange() failed at implicit mutate() step.
> * Problem with `mutate()` column `..1`.
> i `..1 = c(Petal.Width, Species)`.
> i `..1` must be size 150 or 1, not 300.
>
> I'm not sure how to fix the problem either in function or can fix it when using the function.
> Thank you,
> Kai
> 	[[alternative HTML version deleted]]
>
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