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])
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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])
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Output: