Chapter 17 Categorical variables

nominal variables: represent data that are unordered

colors <- c("green", "blue", "yellow")
factor(colors)

## [1] green  blue   yellow
## Levels: blue green yellow

Ordinal variables: ordered, ranked data

If you dont specify, R will do alphatecially

speed <- c("low", "high", "med", "med")

factor(speed, ordered = TRUE)

## [1] low  high med  med 
## Levels: high < low < med

If you specify:

speed <- c("low", "high", "med", "med")

factor(speed,
       levels = c("low", "med", "high"),
       ordered = TRUE)

## [1] low  high med  med 
## Levels: low < med < high

Grab a component from a list

mylist = list(A = c("a, b, d"),
              cinema = ("stars"),
              size = c(1, 2, 3, 4, 4))

Three ways to select a column

mylist[[2]]

## [1] "stars"

mylist[["cinema"]]

## [1] "stars"

mylist$cinema

## [1] "stars"