Introduction to Functions

Intermediate R

Filip Schouwenaars

DataCamp Instructor

Functions

• You already know 'em!
• Create a list: list()
• Display a variable: print()

Black box principle

Black box principle

Black box principle

Black box principle

Black box principle

Black box principle

Black box principle

Call function in R

sd(c(1, 5, 6, 7))

2.629956

values <- c(1, 5, 6, 7)
sd(values)

2.629956

my_sd <- sd(values)
my_sd

2.629956

Function documentation

help(sd)
?sd

sd(x, na.rm = FALSE)

Questions

sd(x, na.rm = FALSE)

• Argument names: x, na.rm
• na.rm = FALSE
• sd(values) works?

Argument matching

sd(x, na.rm = FALSE)

By position

sd(values)

By name

sd(x = values)

na.rm argument

values <- c(1, 5, 6, NA)
sd(values)

NA

sd(x, na.rm = FALSE)

sd(values, TRUE)

2.645751

sd(values, na.rm = TRUE)

2.645751

sd(values) works?

values <- c(1, 5, 6, 7)
sd(values)

2.629956

sd()

Error in is.data.frame(x) : 
argument "x" is missing, with no default

sd(x, na.rm = FALSE)

Useful trick

args(sd)

function (x, na.rm = FALSE) 
NULL

Wrap-up

• Functions work like a black box
• Argument matching: by position or by name
• Function arguments can have defaults

Let's practice!

Intermediate R