CODEWITHSUNDEEP
rfunctiondplyr
Steen Harsted
Steen Harsted

Reputation: 1932

Filter argument in function that defaults to make dplyr::filter() filter nothing

I am building a function that imports excel spreadsheets.

I would like the function to include an argument that contains names of variables that the user is interested in seeing. The values from the argument is used in dplyr::filter() inside the function. I would like the default value of the argument to include everything (i.e. not filter anything away).

Libraries and Data: 

library(tidyverse)
data("iris")

The filter function without any default filter values (this works):

FILTER <- function(data = iris,
                   Filter_Values) {
  data %>%
    filter(Species %in% Filter_Values)
}
FILTER(Filter_Values = c("setosa", "virginica"))

As written above, I would like the Filter_Values argument to default into NOT filtering anything.
This works, but is of course not general: 

FILTER <-
  function(data = iris,
           Filter_Values = c("setosa", "versicolor", "virginica")) {
    data %>%
      filter(Species %in% Filter_Values)
  }

FILTER()

Can you help me find a general term that can do the same. I have tried (and failed) with: 

 Filter_Values = TRUE  
 Filter_Values = c(TRUE)   
 Filter_Values = regex(".*")
 Filter_Values = everything()

Any help appreciated,
Thanks

Upvotes: 2

Views: 1172

Answers (2)

Nicolas2
Nicolas2

Reputation: 2210

Perhaps:

FILTER <- function(data = iris,Filter_Values = NULL) {
    if (missing(Filter_Values)) data
    else data %>% filter(Species %in% Filter_Values)
}

FILTER()

Upvotes: 1

Shinobi_Atobe
Shinobi_Atobe

Reputation: 1963

How about this?

FILTER <-
  function(data = iris,
           Filter_Values = unique(data$Species)) {
    data %>%
      filter(Species %in% Filter_Values)
  }

FILTER()

Upvotes: 1

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