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Select variables (columns) in R using Dplyr

  • Last Updated : 21 Jul, 2021

In this article, we are going to select variables or columns in R programming language using dplyr library.

Dataset in use:

Select column with column name

Here we will use select() method to select column by its name

Syntax:



select(dataframe,column1,column2,.,column n)

Here, data frame is the input dataframe and columns are the columns in the dataframe to be displayed

Example 1: R program to select columns

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush',
                        'sravan','gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada',
                           'guntur','hyd','tenali','hyd'))
  
# select id column from the dataframe by 
# column name
print(select(data1,id))
    
# select name column from the dataframe by
# column name
print(select(data1,name))

Output:

Example 2: R program to select multiple columns

R






# load the library
library(dplyr)
  
# create dataframe with 3 columns 
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush',
                        'sravan','gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada',
                           'guntur','hyd','tenali','hyd'))
  
# select multiple columns from the dataframe
# by column name
print(select(data1,id,name,address))

Output:

Select column(s) by position

We can also use the column position and get the column using select() method. Position starts with 1.

Syntax:

select(dataframe,column1_position,column2_position,.,column n_position)

where, dataframe is the input dataframe and column position is an column number

For selecting multiple columns we can use range operator “;” to select columns by their position

Syntax:

select(dataframe,start_position:end_position)

where, dataframe is the input dataframe, start_position  is a column number starting position and end_position  is a column number ending position



Example 1: R program to select particular column by column position

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush',
                        'sravan','gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada',
                           'guntur','hyd','tenali','hyd'))
  
# select first column by column position
print(select(data1,1))
  
# select third column by column position
print(select(data1,3))
   

Output:

Example 2: R program to select multiple columns by positions

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns 
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada','guntur',
                           'hyd','tenali','hyd'))
  
# select multiple column by column position
print(select(data1,1,2))

Output:

Example 3: R program to select multiple columns by position with range operator

R






# load the library
library(dplyr)
  
# create dataframe with 3 columns 
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada','guntur',
                           'hyd','tenali','hyd'))
  
# select multiple column by column 
# position with : operator
print(select(data1,1:3))

Output:

Select column which contains a value or matches a pattern

Here, we will display the column values based on values or pattern present in the column 

Method 1: Using contains() 

Display the column that contains the given sub string

Syntax:

select(dataframe,contains(‘sub_string’))

Here, dataframe is the input dataframe and sub_string is the string present in the column name

Example: R program to select column based on substring

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns 
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada','guntur',
                           'hyd','tenali','hyd'))
  
# select column that contains am
print(select(data1,contains('am')))
  
# select column that contains d
print(select(data1,contains('d')))
  
# select column that contains dd
print(select(data1,contains('dd')))

Output:



Method 2: Using matches()

It will check and display the column that contains the given sub string

select(dataframe,matches(‘sub_string’))

Here, dataframe is the input dataframe and sub_string is the string present in the column name

Example: R program to select column based on substring

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns 
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada','guntur',
                           'hyd','tenali','hyd'))
  
# select column that matches with  am
print(select(data1,matches('am')))
  
# select column that matches with d
print(select(data1,matches ('d')))
  
# select column that matches with  dd
print(select(data1,matches ('dd')))

Output:

Select column which starts with or ends with certain character

Here we can also select columns based on starting and ending characters.

  • starts_with() is used to return the column that starts with the given character.

Syntax:



select(dataframe,starts_with(‘substring’))

Where, dataframe is the input dataframe and substring is the character/string that starts with it

  • ends_with() is used to return the column that ends with the given character.

Syntax:

select(dataframe,ends_with(‘substring’))

where, dataframe is the input dataframe and substring is the character/string that ends with it

Example 1: R program to display columns that starts with a character/substring

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada','guntur',
                           'hyd','tenali','hyd'))
  
# select column that starts with n
print(select(data1,starts_with('n')))
  
# select column that starts with add
print(select(data1,starts_with('add')))

Output:

Example 2: R program to select column that ends with a given string or character



R




# load the library
library(dplyr)
  
# create dataframe with 3 columns id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali','vijayawada',
                           'vijayawada','guntur','hyd','tenali','hyd'))
  
# select column that ends with ss
print(select(data1,ends_with('ss')))
  
# select column that ends with d
print(select(data1,ends_with('d')))

Output:

Select all columns

We can select all the columns in the data frame by using everything() method.

Syntax:

select(dataframe,everything())

Example: R program to select all columns

R




# load the library
library(dplyr)
  
# create dataframe with 3 columns
# id,name and address
data1=data.frame(id=c(1,2,3,4,5,6,7,1,4,2),
                   
                 name=c('sravan','ojaswi','bobby','gnanesh',
                        'rohith','pinkey','dhanush','sravan',
                        'gnanesh','ojaswi'),
                   
                 address=c('hyd','hyd','ponnur','tenali',
                           'vijayawada','vijayawada','guntur',
                           'hyd','tenali','hyd'))
  
# select all columns using everything method
print(select(data1,everything()))

Output:




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