Removing Columns of data.table by Index in R (2 Examples)
In this tutorial, I’ll illustrate how to exclude certain columns from a data.table by indexing them in the R programming language.
Setting up the Examples
First, we need to install and load the data.table package.
install.packages("data.table") # Install data.table package library("data.table") # Load data.table |
We use the iris dataset to illustrate how to delete certain data.table columns by their indices.
data(iris) # Load iris data set iris_DT <- data.table::copy(iris) # Replicate iris data set setDT(iris_DT) # Convert iris to a data.table head(iris_DT) # Print the head of the data # Sepal.Length Sepal.Width Petal.Length Petal.Width Species # 1: 5.1 3.5 1.4 0.2 setosa # 2: 4.9 3.0 1.4 0.2 setosa # 3: 4.7 3.2 1.3 0.2 setosa # 4: 4.6 3.1 1.5 0.2 setosa # 5: 5.0 3.6 1.4 0.2 setosa # 6: 5.4 3.9 1.7 0.4 setosa |
Example 1: Removing Column By Indexing
We exclude column number three (Petal.Length) from the data using the following code.
iris_DT_2 <- data.table::copy(iris_DT) # Replicate data set iris_DT iris_DT_3 <- iris_DT_2[ , -c(3) ] # Remove column 3 head(iris_DT_3) # Print the head of the new data # Sepal.Length Sepal.Width Petal.Width Species # 1: 5.1 3.5 0.2 setosa # 2: 4.9 3.0 0.2 setosa # 3: 4.7 3.2 0.2 setosa # 4: 4.6 3.1 0.2 setosa # 5: 5.0 3.6 0.2 setosa # 6: 5.4 3.9 0.4 setosa |
Example 2: Removing Several Columns By Indexing
We delete columns number three (Petal.Length) and five (Species) from the data with the following lines of R code.
iris_DT_4 <- data.table::copy(iris_DT) # Replicate data set iris_DT iris_DT_5 <- iris_DT_4[ , -c(3, 5) ] # Remove columns 3 and 5 head(iris_DT_5) # Print the head of the new data # Sepal.Length Sepal.Width Petal.Width # 1: 5.1 3.5 0.2 # 2: 4.9 3.0 0.2 # 3: 4.7 3.2 0.2 # 4: 4.6 3.1 0.2 # 5: 5.0 3.6 0.2 # 6: 5.4 3.9 0.4 |
Further Resources
In the following, you may find some further resources that are similar to the topic of this post:
- How to Delete Column & Row Names of Matrix
- How to Delete Several Variables from data.table
- Delete Column Names from Data Frame
- Delete Variables with Duplicate Column Names in R
Note: This article was created in collaboration with Anna-Lena Wölwer. Anna-Lena is a researcher and programmer who creates tutorials on statistical methodology as well as on the R programming language. You may find more info about Anna-Lena and her other articles on her profile page.