CODEWITHSUNDEEP
r
mirirai
mirirai

Reputation: 1409

How to check if an R object has a certain attribute?

How can I check if an R object has a certain attribute? For example, I would like to check if a vector has a "labels" attribute. How can I do this? Exists already a function that does that?

my_vector <- c(1, 2, 3)
my_vector_labelled <- `attr<-`(my_vector, "labels", c(a = 1, b = 2, c = 3))

let's assume there is a function named has_attribute(x, attr). The the expected result would be:

> has_attribute(my_vector, "labels")
 FALSE
> has_attribute(my_vector_labelled, "labels")
 TRUE

Upvotes: 3

Views: 1441

Answers (3)

Rui Barradas
Rui Barradas

Reputation: 76402

Use attributes.

my_vector <- c(1, 2, 3)
my_vector_labelled <- `attr<-`(my_vector, "labels", c(a = 1, b = 2, c = 3)) 

attributes(my_vector)
#> NULL
names(attributes(my_vector_labelled))
#> [1] "labels"

has_attribute <- function(x, which){
  which %in% names(attributes(x))
}
has_attribute(my_vector_labelled, "labels")
#> [1] TRUE

Created on 2022-03-31 by the reprex package (v2.0.1)

Upvotes: 2

akrun
akrun

Reputation: 887118

There is a function available in package

> library(BBmisc)
> hasAttributes(my_vector_labelled, "labels")
[1] TRUE
> hasAttributes(my_vector, "labels")
[1] FALSE

Upvotes: 2

r2evans
r2evans

Reputation: 160447

Two ways:

  • %in% names(attributes(..):

    "labels" %in% names(attributes(my_vector))
# [1] FALSE
"labels" %in% names(attributes(my_vector_labelled))
# [1] TRUE

  • is.null(attr(..,"")):

    is.null(attr(my_vector, "labels"))
# [1] TRUE                                   # NOT present
is.null(attr(my_vector_labelled, "labels"))
# [1] FALSE                                  # present

    (Perhaps !is.null(attr(..)) is preferred?)

Upvotes: 6

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