Lære Levels in Factors

Definition

Levels in a factor represent the set of distinct categories that the factor can take.

Viewing Levels

The levels() function shows all unique values stored in a factor.

Example


              12345
            
curr_f <- factor(c('USD', 'EUR', 'AUD', 'NOK', 
                   'CHF', 'EUR', 'AUD', 'EUR'))

# Display all levels
levels(curr_f)

Ordered Factors

In some cases, categories have a natural order (e.g., "short" < "medium" < "tall"). Factors can be declared as ordered by setting ordered = TRUE.

Example


              12345
            
sizes <- c('short', 'tall', 'medium',
           'medium', 'short', 'tall')

# Ordered factor (alphabetical order)
factor(sizes, ordered = TRUE)

Custom Ordering

By default, R orders levels in alphabetical order, which may not always match the intended hierarchy. You can define a specific order by passing a vector of levels in the desired sequence.

Example


              123456
            
sizes <- c('short', 'tall', 'medium',
           'medium', 'short', 'tall')
order <- c('short', 'medium', 'tall')

# Ordered factor (correct order)
factor(sizes, ordered = TRUE, levels = order)

This ensures the order matches your intended meaning.

Opgave

Swipe to start coding

You have a vector of grades ranging from 'A' to 'F'. You're tasked with converting this into an ordered factor with the sequence 'F < D < C < B < A':

Convert the grades vector to a factor, capturing the required order, and store it in the grades_f variable.
Display the entire grades_f variable.

Løsning

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Sektion 1. Kapitel 23

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Definition

Levels in a factor represent the set of distinct categories that the factor can take.

Viewing Levels

The levels() function shows all unique values stored in a factor.

Example


              12345
            
curr_f <- factor(c('USD', 'EUR', 'AUD', 'NOK', 
                   'CHF', 'EUR', 'AUD', 'EUR'))

# Display all levels
levels(curr_f)

Ordered Factors

In some cases, categories have a natural order (e.g., "short" < "medium" < "tall"). Factors can be declared as ordered by setting ordered = TRUE.

Example


              12345
            
sizes <- c('short', 'tall', 'medium',
           'medium', 'short', 'tall')

# Ordered factor (alphabetical order)
factor(sizes, ordered = TRUE)

Custom Ordering

By default, R orders levels in alphabetical order, which may not always match the intended hierarchy. You can define a specific order by passing a vector of levels in the desired sequence.

Example


              123456
            
sizes <- c('short', 'tall', 'medium',
           'medium', 'short', 'tall')
order <- c('short', 'medium', 'tall')

# Ordered factor (correct order)
factor(sizes, ordered = TRUE, levels = order)

This ensures the order matches your intended meaning.

Opgave

Swipe to start coding

You have a vector of grades ranging from 'A' to 'F'. You're tasked with converting this into an ordered factor with the sequence 'F < D < C < B < A':

Convert the grades vector to a factor, capturing the required order, and store it in the grades_f variable.
Display the entire grades_f variable.

Løsning

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Var alt klart?

Tak for dine kommentarer!

Sektion 1. Kapitel 23

single