Select Subset of DataTable Columns in R

In this article, we will discuss how to select a subset of data table columns in R programming language.

Let's create a data table using a matrix. First, we need to load data.table package in the working space.

Installation

install.packages("data.table")                         

Loading

library("data.table") 

Dataset in use:

Method 1: Using []

We can select a subset of datatable columns by index operator - []

Syntax:

datatable[ ,  c(columns), with = FALSE]

Where,

• datatable is the input data table
• columns are the columns in the datatable to be selected
• with =FALSE is an optional parameter

Example: R program to select subset of columns from the data table

# load data.table package
library("data.table")

# create data table with matrix with 20 elements
# 4 rows and 5 columns
data= data.table(matrix(1:20, nrow=4,ncol = 5))             

# display the subset that include v1 and v3 columns
print(data[ ,  c("V1", "V3"), with = FALSE])

# display the subset that include v1 , v2 and v3 columns
print(data[ ,  c("V1","V2", "V3"), with = FALSE])

# display the subset that include v2,v3,v4 and v5 columns
print(data[ ,  c("V2", "V3","V4","V5"), with = FALSE])

Output:

Method 2: Using !

Using ! operator before columns can be enough to get the job done by this approach. Here we are not including the subset that is selected from the data table

Syntax:

datatable[ ,  !c(columns), with = FALSE]

where,

• datatable is the input data table
• columns are the columns in the datatable to be selected

Example: R program to select columns from datatable

# load data.table package
library("data.table")

# create data table with matrix with 20 elements
# 4 rows and 5 columns
data= data.table(matrix(1:20, nrow=4,ncol = 5))             

# display the subset that exclude v1 and v3 columns
print(data[ ,  !c("V1", "V3"), with = FALSE])

# display the subset that exclude  v1 , v2 and v3 columns
print(data[ ,  !c("V1","V2", "V3"), with = FALSE])

# display the subset that exclude v2,v3,v4 and v5 columns
print(data[ ,  !c("V2", "V3","V4","V5"), with = FALSE])

Output: