Functional programming in R

Gevorderd functioneel programmeren met purrr

Colin Fay

Data Scientist & R Hacker at ThinkR

About computation in R

"To understand computations in R, two slogans are helpful:

- Everything that exists is an object.

- Everything that happens is a function call."    -John Chambers

class(`+`)

"function"

class(`<-`)

"function"
Gevorderd functioneel programmeren met purrr

R as a functional programming language

Functions can be

  • manipulated

  • stored in a variable

  • lambda

 

  • stored in a list

  • arguments of a function

  • returned by a function

Gevorderd functioneel programmeren met purrr

About "pure functions"

In a pure function:

  • output only depends on input

  • no "side-effect"

# Output depends only on inputs
# No side effect
sum(1:10)

55

mean(1:100)

50.5
Gevorderd functioneel programmeren met purrr

Impure functions are useful

Impure functions:

  • Depend on environment

  • Have "side-effects"

# Outputs depends of environment 
Sys.Date()

"2018-10-04"

# Side effect only
write.csv(iris, "iris.csv")
Gevorderd functioneel programmeren met purrr

Read more about functional programming

Gevorderd functioneel programmeren met purrr

Let's practice!

Gevorderd functioneel programmeren met purrr

Preparing Video For Download...