3 Manipulating Columns

Select columns	`select()`, `pull()`
Arrange columns	`relocate()`, `select()`
Add columns	`mutate()`, `transmute()`, `bind_cols()`
Rename columns	`rename()`

Please copy the following code and paste them into a script in the RStudio. We will walk through them with the visual explanations from the dplyr cheat sheet.

Input

# Sample code from the dplyr cheat sheet
## 3.1 Select columns
pullmt=pull(mtcars, wt)
selectmt=select(mtcars, mpg, wt)

## 3.2 Arrange columns
relocatemt=relocate(mtcars, mpg, cyl, .after = last_col())

## 3.3 Add columns
mutmt=mutate(mtcars, gpm = 1 / mpg)
tmt=transmute(mtcars, gpm = 1 / mpg)

### A showcase for bind_cols
x <- data.frame(
  A = c('a', 'b', 'c'), 
  B = c('t', 'u', 'v'),
  C = c(1, 2, 3))
x
y <- data.frame(
  E = c('a', 'b', 'd'), 
  G = c('t', 'u', 'w'), #skip F because F = FALSE, so it's best not to use that letter.
  H = c(3, 2, 1))
y
# You have to make sure the binding is meaningful by yourself. 
# This is not the same as joins
bind_cols(x, y) 

## 3.4 Rename columns
rename(cars, distance = dist)

Practice 2

iris is a data frame with 150 cases (rows) and 5 variables (columns) named Sepal.Length, Sepal.Width, Petal.Length, Petal.Width, and Species. Make a new data frame which contains only Species and the ratio of Petal.Width and Petal.Length.

Click here for solution

my_iris1 <- iris %>% mutate(Petal.Width.Length.Ratio = Petal.Width/Petal.Length) %>% select(Species, Petal.Width.Length.Ratio)

This page is meant to introduce functions that help manipulate columns.