Function name in single quotes in R

This may be a stupid question, but I've been worried for a long time. I've seen people use single quotes to surround a function name when they define a function. I think about the benefits of this all the time. Below is a naive example

'row.mean' <- function(mat){
    return(apply(mat, 1, mean))


Thanks in advance!


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1 answer

Based on Richard's suggestion, back ticks allow characters in names that are not normally allowed. Cm:

`add+5` <- function(x) {return(x+5)}


defines a function, but

add+5 <-  function(x) {return(x+5)}



Error in add + 5 <- function(x) { : object 'add' not found


To call the function, you also need to explicitly use back ticks.

> `add+5`(3)
[1] 8


To see the code for this function, just call it with no arguments:

> `add+5`
function(x) {return(x+5)}


See also this comment which deals with the difference between indentation and quotation marks in naming:

Note: The use of reverse ticks is much more general. For example, in a dataframe, you can have columns with integers (perhaps using reshape::cast

for integer factors).

For example:

test = data.frame(a = "a", b = "b")
names(test) <- c(1,2)


and to retrieve those columns, you can use a backward line in combination with an operator $

, for example:

> test$1
Error: unexpected numeric constant in "test$1"



> test$`1`
[1] a
Levels: a


Ridiculously, you can't use back ticks when assigning column names to a data frame; the following doesn't work:

test = data.frame(`1` = "a", `2` = "b")


And responding to statechular comments, here are two more use cases.

In the fix functions

Using a symbol %

, we can naively define the dot product between vectors x

and y


`%.%` <- function(x,y){

    sum(x * y)



which gives

> c(1,2) %.% c(1,2)
[1] 5


see below:

Spare functions

Here's a great answer that demonstrates what it is: What are replacement functions in R?



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