How can I create a function defined by parts in RStudio?

[heitor]

Hi everyone,

I want to know what I need to do to create a function defined by parts in RStudio, particularly the structure of the code. The data is not important at the moment, you can show me anything.

Thanks for all,

Heitor.

[nirgrahamuk]

Creating functions in Rstudio is no different from creating them in R.
Here is a guide to doing it in R.
https://swcarpentry.github.io/r-novice-inflammation/02-func-R/

[heitor]

Thanks for the link, but i wanna do "function defined by parts".

[nirgrahamuk]

I have no idea what that means, can you describe it or provide some example?

[heitor]

Of course..

Like this: f(x) = 0, if x > 1
x + 2, if x < 0

In this situation, is a exemple.
Here you can learn more about : [https://www.sangakoo.com/en/unit/functions-defined-by-parts#:~:text=A%20function%20defined%20by%20parts,value%20of%20the%20independent%20variable.]

[nirgrahamuk]

R has an ifelse() function.
https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/ifelse

[heitor]

I'll try ifelse, but a i dont know if this code could be help me..
I need to show my results in a graph later..

[StatSteph]

For the example at the link which has 3 parts, I would do something like this:

#https://www.sangakoo.com/en/unit/functions-defined-by-parts#:~:text=A%20function%20defined%20by%20parts,value%20of%20the%20independent%20variable.%5D
f <- function(x){
  dplyr::case_when(
    x <= -3 ~ -x-1,
    x>-1 & x<1 ~3,
    x >=1 ~ x-2,
    TRUE ~ NA_real_ # all other cases
  )
}

f(-4)
#> [1] 3
f(-2)
#> [1] NA
f(.5)
#> [1] 3
f(1)
#> [1] -1

^{Created on 2020-10-04 by the reprex package (v0.3.0)}