Return in R - r - learn r - r programming
- Many times, we require our functions to do some processing and return back the result.
- This is done with the return() function in R.
- In other words transmit a value back to the caller by explicitly calling return().
- Without this call, the value of the last executed statement will be returned by default.
Syntax
return(expression)
- The value returned from a function can be any valid object.
Example
- Here is an example which will return whether a given number is positive, negative or zero.
check <- function(x) {
if (x >0) {
result <- "Positive"
}
elseif (x <0) {
result <- "Negative"
}
else {
result <- "Zero"
}
return(result)
}
Here, given sample codes.
>check(1)
[1] "Positive"
>check(-10)
[1] "Negative"
>check(0)
[1] "Zero"
Functions without return()
- If there are no explicit returns from a function, the value of the last evaluated expression is returned automatically in R.
- For example, the following is equivalent to the above function.
check <- function(x) {
if (x >0) {
result <- "Positive"
}
elseif (x <0) {
result <- "Negative"
}
else {
result <- "Zero"
}
result
}
- We generally use explicit return() functions to return a value immediately from a function.
- If it is not the last statement of the function, it will prematurely end the function bringing the control to the place from which it was called.
check <- function(x) {
if (x>0) {
return("Positive")
}
elseif (x<0) {
return("Negative")
}
else {
return("Zero")
}
}
- In the above example, if x > 0, the function immediately returns "Positive" without evaluating rest of the body.
Multiple Returns
- The return() function can return only a single object. If we want to return multiple values in R, we can use a list (or other objects) and return it.
- Following is an example.
multi_return<- function() {
my_list<- list("color" = "red", "size" = 20, "shape" = "round")
return(my_list)
}
- Here, we create a list my_list with multiple elements and return this single list.
> a <- multi_return()
>a$color
[1] "red"
>a$size
[1] 20
>a$shape
[1] "round"