Worksheet 5 - User-defined Functions - Answers

1. Describe the components and arguments of the following function.

largest <- function(x,y,z){
  a <- c(x,y,z)
  l <- which.max(a)
  paste(a[l],"is the largest number")
}

Example

largest(6,57,5)

## [1] "57 is the largest number"

Explanation

The function largest takes in three numeric arguments x, y, and z. The function first line finds the index of the largest numeric value in the vector. The final line outputs the index of the largest number, with a bit of text.

2. Create and test a function that takes in two vectors and determines which is the longer vector.

a <- c(5,6,7,8,9)
b <- c(1:20)

longs <- function(x,y){
  if(length(x) > length(y)){return(paste("x is longer"))}
  if(length(x) < length(y)){return(paste("y is longer"))}
  if(length(x) == length(y)){return(paste("x and y are the same length"))}  
}

longs(a,b)

## [1] "y is longer"