CODEWITHSUNDEEP
r
GarlicSTAT
GarlicSTAT

Reputation: 243

Check whether the variable is a result of a specific function in R

For example,

example.function = function(x){
    return (x+1)}

and then I do:

test = example.function(2)

How can I check whether the variable test is the result of the function example.function ?

Upvotes: 3

Views: 61

Answers (2)

ThomasIsCoding
ThomasIsCoding

Reputation: 102920

Maybe you can try attr<- + sys.call (or match.call)

example.function = function(x) `attr<-`(x+1,"function call", sys.call()[[1]]))

such that

> test
[1] 3
attr(,"function call")
[1] "example.function"

Upvotes: 3

Allan Cameron
Allan Cameron

Reputation: 174641

If you are writing the function, you can use attributes

example.function = function(x) `attr<-`(x + 1, "created by", "example.function")

So that the result is still a completely standard numeric object, but it has an additional attribute:

x <- example.function(2)

x
#> [1] 3
#> attr(,"created by")
#> [1] "example.function"

A somewhat more sophisticated method would be to hide the attribute by using S3 dispatching, and creating a specific test function:

example.function <- function(x) `attr<-`(x + 1, "class", "special")

print.special <- function(x) print(as.numeric(x))

is.special <- function(x) class(x) == "special"

x <- example.function(2)

x
#> [1] 3

is.special(x)
#> [1] TRUE

If you are asking whether you can tell more generally if an object has come from any particular function, then the answer is no.

Upvotes: 3

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