How to Subset a Data Frame by a Column in R

Creating a subset (filtering) a data frame by a column is a common data manipulation task.

Code used in this clip:

# Load some data
df = mtcars
head(df)

# Create a logical vector from a column
logical = df$cyl == 6
logical

# Use the index to select the desired rows
df[logical, ]

# All in one step:
df[df$cyl == 6, ]

# Subset with the dplyr library using filter
library(dplyr)

filter(df, cyl == 6)

Code Clips are basic code explanations in 2 minutes or less. They are intended to be short reference guides that provide quick breakdowns and copy/paste access to code needed to accomplish common data science tasks. Think Stack Overflow with a video explanation.

* Note: YouTube does not allow greater than or less than symbols in the text description, so the code above will not be exactly the same as the code shown in the video! For R that means I may use = for assignment and the special Unicode large ＜ and ＞ symbols in place of the standard sized ones for dplyr pipes and comparisons. These special symbols should work as expected for R code on Windows, but may need to be replaced with standard greater than and less than symbols for other operating systems.