CODEWITHSUNDEEP
rfunction
M_Neelakandan
M_Neelakandan

Reputation: 79

What does '%!in%' <- function(x,y)!('%in%'(x,y)) mean?

I'm trying to understand this:

'%!in%' <- function(x,y)!('%in%'(x,y))

Is '%!in%' just the name of the function? What are the uses/benefits of giving a function a name like this?

What role does !('%in%'(x,y)) play in the function?

Upvotes: 0

Views: 83

Answers (1)

Konrad Rudolph
Konrad Rudolph

Reputation: 545766

The use of naming a function like %…% is that it can be used as an infix operator:

4 %in% (1 : 10)
# TRUE

4 %!in% (1 : 10)
# FALSE

Since %…% isn’t a valid name, it needs to be backtick-quoted (with `…`) when used as a name (e.g. when defining it or when using it as a regular function):

# Definition:
`%!in%` = function (x, y) ! x %in% y

# Using function call syntax
`%in%`(4, 1 : 10)

# Passing it to a different function
lapply(c(2, 4, 20), `%in%`, 1 : 10)

For historical reasons/backwards compatibility, R also allows you to use regular quotes ('…' or "…") instead of backticks in specific situations. However, this usage is confusing and not recommended!

Upvotes: 4

Related Questions