Problem using dataframes columns in functions

[Poumon]

Hi everyone, I'm starting using R and I encounter a problem that I can't explain:

 filter_table_and_extract_column <- function(data,column_to_filter_by_value,value, column_to_extract){
 extracted_column <-(data %>% filter(column_to_filter_by_value == value))$column_to_extract
Return(extracted_column)

Error message:

`Preformatted text`Error in { (1-get_signature_infos.R#152): task 1 failed - "Problem with `filter()` input `..1`.
✖ object 'ONTOLOGY' not found
ℹ Input `..1` is `column_to_filter_by_value == value`."`Preformatted text`

In this case, the variable : column_to_filter_by_value is ONTOLOGY

[Poumon]

Ok I understand now that it's a non standard evaluation. So I realized that I can use quote(), unquote() and !!

I tried to write it like this but still doesn't do what I want:

filter_table_and_extract_column <- function(data,column_to_filter_by_value,value, column_to_extract){
  column_to_filter_by_value <- enquo(column_to_filter_by_value)
  column_to_extract <- as_label(enquo(column_to_extract))
  extracted_column <- (data %>% filter(!!column_to_filter_by_value == value))[[column_to_extract]]
  return(extracted_column)
}

[andresrcs]

library(dplyr)

filter_table_and_extract_column <- function(data, column_to_filter_by_value, value, column_to_extract) {
        data %>%
            filter({{column_to_filter_by_value}} == {{value}}) %>% 
            pull({{column_to_extract}})
}

filter_table_and_extract_column(iris, Species, "setosa", Sepal.Length)
#>  [1] 5.1 4.9 4.7 4.6 5.0 5.4 4.6 5.0 4.4 4.9 5.4 4.8 4.8 4.3 5.8 5.7 5.4 5.1 5.7
#> [20] 5.1 5.4 5.1 4.6 5.1 4.8 5.0 5.0 5.2 5.2 4.7 4.8 5.4 5.2 5.5 4.9 5.0 5.5 4.9
#> [39] 4.4 5.1 5.0 4.5 4.4 5.0 5.1 4.8 5.1 4.6 5.3 5.0

^{Created on 2021-02-13 by the reprex package (v1.0.0)}

[Poumon]

@andresrcs

Thanks a lot, clear solution and it works perfectly !

[williaml]

More about curly-curly:

rlang 0.4.0