Lære Manipulating Columns

Data frames are flexible: you can add, remove, and rename columns as needed.

Adding Columns

To add a new column, assign a vector of values to a new column name. You can use either the dollar ($) sign or square brackets with quotes.

Example


              12345678
            
name <- c("Alex", "Julia", "Finn")
age <- c(24, 43, 32)
gender <- c("M", "F", "M")
test <- data.frame(name, age, gender)

# Adding a new column with job titles
test$job <- c("Teacher", "Doctor", "Manager")
test

You could also do the same with:

test[, "Job"] <- c("Teacher", "Doctor", "Manager")

Note

The length of the vector you add must match the number of rows in the data frame.

Deleting Columns

To remove one or more columns, use the subset() function with the select = -... argument.

Example


              12345678910
            
name <- c("Alex", "Julia", "Finn")
age <- c(24, 43, 32)
gender <- c("M", "F", "M")
test <- data.frame(name, age, gender)
test$job <- c('Teacher', 'Doctor', 'Manager')

# Drop a single column
subset(test, select = -job)
# Drop multiple columns
subset(test, select = -c(age, gender))

Renaming Columns

To rename columns, use the colnames() function. The syntax is the same as with matrices:

colnames(data) <- new_names

Opgave

Swipe to start coding

You have a data frame store containing information on items and their prices from a small furniture store:

items	prices
Sofa	340
Armchair	150
Dining table	115
Dining chair	45
Bookshelf	160

You need to transform it into this table:

Item	Price	Sold
Sofa	340	67
Armchair	150	81
Dining table	115	79
Dining chair	45	76
Bookshelf	160	42

Follow the next steps:

Rename the columns names of store to c('Item', 'Price').
Add new column Sold with the values of c(67, 81, 79, 76, 42).
Output modified data frame.

Løsning

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Sektion 1. Kapitel 38

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Data frames are flexible: you can add, remove, and rename columns as needed.

Adding Columns

To add a new column, assign a vector of values to a new column name. You can use either the dollar ($) sign or square brackets with quotes.

Example


              12345678
            
name <- c("Alex", "Julia", "Finn")
age <- c(24, 43, 32)
gender <- c("M", "F", "M")
test <- data.frame(name, age, gender)

# Adding a new column with job titles
test$job <- c("Teacher", "Doctor", "Manager")
test

You could also do the same with:

test[, "Job"] <- c("Teacher", "Doctor", "Manager")

Note

The length of the vector you add must match the number of rows in the data frame.

Deleting Columns

To remove one or more columns, use the subset() function with the select = -... argument.

Example


              12345678910
            
name <- c("Alex", "Julia", "Finn")
age <- c(24, 43, 32)
gender <- c("M", "F", "M")
test <- data.frame(name, age, gender)
test$job <- c('Teacher', 'Doctor', 'Manager')

# Drop a single column
subset(test, select = -job)
# Drop multiple columns
subset(test, select = -c(age, gender))

Renaming Columns

To rename columns, use the colnames() function. The syntax is the same as with matrices:

colnames(data) <- new_names

Opgave

Swipe to start coding

You have a data frame store containing information on items and their prices from a small furniture store:

items	prices
Sofa	340
Armchair	150
Dining table	115
Dining chair	45
Bookshelf	160

You need to transform it into this table:

Item	Price	Sold
Sofa	340	67
Armchair	150	81
Dining table	115	79
Dining chair	45	76
Bookshelf	160	42

Follow the next steps:

Rename the columns names of store to c('Item', 'Price').
Add new column Sold with the values of c(67, 81, 79, 76, 42).
Output modified data frame.

Løsning

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Var alt klart?

Tak for dine kommentarer!

Sektion 1. Kapitel 38

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