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In R, you can extract specific columns from a data frame by specifying the column names within square brackets after the name of the data frame. For example, if you wanted to extract the first two columns from a data frame called “data”, you could specify the command as “data[,c(1,2)]”. This will return a subset of the data frame with just the specified columns. You can also use the “$” operator to extract columns by name. For example, “data$column1” will return the values from the column named “column1” in the data frame “data”.
You can use the following methods to extract specific columns from a data frame in R:
Method 1: Extract Specific Columns Using Base R
df[c('col1', 'col3', 'col4')]
Method 2: Extract Specific Columns Using dplyr
library(dplyr)
df %>%
select(col1, col3, col4)
The following examples show how to use each method with the following data frame in R:
#create data frame df <- data.frame(team=c('A', 'B', 'C', 'D', 'E'), points=c(99, 90, 86, 88, 95), assists=c(33, 28, 31, 39, 34), rebounds=c(30, 28, 24, 24, 28), steals=c(9, 12, 4, 7, 8)) #view data frame df team points assists rebounds steals 1 A 99 33 30 9 2 B 90 28 28 12 3 C 86 31 24 4 4 D 88 39 24 7 5 E 95 34 28 8
Method 1: Extract Specific Columns Using Base R
The following code shows how to extract the team, assists, and rebounds columns using base R:
#select 'team', 'assists' and 'rebounds' columns
df[c('team', 'assists', 'rebounds')]
team assists rebounds
1 A 33 30
2 B 28 28
3 C 31 24
4 D 39 24
5 E 34 28
Notice that each of the columns we specified have been extracted from the data frame.
Also note that you can extract these columns by index position as well:
#select columns in index positions 1, 3 and 4
df[c(1, 3, 4)]
team assists rebounds
1 A 33 30
2 B 28 28
3 C 31 24
4 D 39 24
5 E 34 28
This syntax extracts the columns in column index positions 1, 3 and 4.
Method 2: Extract Specific Columns Using dplyr
The following code shows how to extract the team, assists, and rebounds columns using the select() function from the package:
library(dplyr)
#select 'team', 'assists' and 'rebounds' columns
df %>%
select(team, assists, rebounds)
team assists rebounds
1 A 33 30
2 B 28 28
3 C 31 24
4 D 39 24
5 E 34 28
Also note that you can extract these columns by index position as well:
library(dplyr)
#select 'team', 'assists' and 'rebounds' columns
df %>%
select(1, 3, 4)
team assists rebounds
1 A 33 30
2 B 28 28
3 C 31 24
4 D 39 24
5 E 34 28 This syntax extracts the columns in column index positions 1, 3 and 4.
The following tutorials explain how to perform other common tasks in R: