Functional programming in R

Intermediate Functional Programming with 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"
Intermediate Functional Programming with 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

Intermediate Functional Programming with 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
Intermediate Functional Programming with 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")
Intermediate Functional Programming with purrr

Read more about functional programming

Intermediate Functional Programming with purrr

Let's practice!

Intermediate Functional Programming with purrr

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