refer to quoted column name in a function in R-CodePudding

I want to use the na_omit function from the collapse package in a user-defined function. na_omit requires a column name to be in quotes as one of its arguments. If I didn't need the column name in quotes, I could just refer to the column name in double braces, {{col}}, as mentioned in this vignette, "Programming with dplyr". If I refer to the column using the glue package, such as glue::glue("{col}"), I receive errors.

Here is a reprex:

my_df <-
  data.frame(
    matrix(
      c(
        "V9G","Blue",
        NA,"Red",
        "J4C","White",
        NA,"Brown",
        "F7B","Orange",
        "G3V","Green"
      ),
      nrow = 6,
      ncol = 2,
      byrow = TRUE,
      dimnames = list(NULL,
                      c("color_code", "color"))
    ),
    stringsAsFactors = FALSE
  )

library(collapse)
library(dplyr)
library(glue)

my_func <- function(df, col){
  df %>% 
    collapse::na_omit(cols = c(glue("{col}"))) #Here is the code that fails
}

my_func(my_df, color_code)

How should I refer to a quoted column name that's a parameter and an argument of a function within a user-defined function in R?

CodePudding user response：

In general, collapse is mostly standard evaluation and its NSE features are based upon base R, so most of the rlang and glue stuff etc. won't work, but you will have simpler and faster code. As suggested, for a single column, a solution would be function(df, col) { col <- as.character(substitute(col)); ...; } i.e. use substitute() to capture the expression and as.character or all.vars to extract the variables. For multiple columns a general solution is wrapping fselect e.g.

library(collapse)
my_func <- function(df, ...) {
  cols <- fselect(df, ..., return = "indices")
  na_omit(df, cols = cols) 
}

my_func(wlddev, PCGDP:GINI, POP) |> head()
#>   country iso3c       date year decade                region
#> 1 Albania   ALB 1997-01-01 1996   1990 Europe & Central Asia
#> 2 Albania   ALB 2003-01-01 2002   2000 Europe & Central Asia
#> 3 Albania   ALB 2006-01-01 2005   2000 Europe & Central Asia
#> 4 Albania   ALB 2009-01-01 2008   2000 Europe & Central Asia
#> 5 Albania   ALB 2013-01-01 2012   2010 Europe & Central Asia
#> 6 Albania   ALB 2015-01-01 2014   2010 Europe & Central Asia
#>                income  OECD    PCGDP LIFEEX GINI       ODA     POP
#> 1 Upper middle income FALSE 1869.866 72.495 27.0 294089996 3168033
#> 2 Upper middle income FALSE 2572.721 74.579 31.7 453309998 3051010
#> 3 Upper middle income FALSE 3062.674 75.228 30.6 354950012 3011487
#> 4 Upper middle income FALSE 3775.581 75.912 30.0 338510010 2947314
#> 5 Upper middle income FALSE 4276.608 77.252 29.0 335769989 2900401
#> 6 Upper middle income FALSE 4413.297 77.813 34.6 260779999 2889104

^{Created on 2022-02-03 by the reprex package (v2.0.1)}

CodePudding user response：

You have to provide col name as a character, like:

my_func <- function(df, col){
  df %>% 
    collapse::na_omit(cols = c(glue("{col}"))) #Here is the code that fails
}

my_func(my_df, col = "color_code")