There are different ways to extract columns from a data frame in R:
- using index value
- column name
- using
$
to access specific column
Example 1: Use Index Value to Access Dataframe Column in R
# Create a data frame
dataframe1 <- data.frame (
Name = c("Juan", "Alcaraz", "Simantha"),
Age = c(22, 15, 19),
Vote = c(TRUE, FALSE, TRUE)
)
# pass index value 1 to access first column
print(dataframe1[1])
# pass index value 3 to access third column
print(dataframe1[3])
Output
Name 1 Juan 2 Alcaraz 3 Simantha Vote 1 TRUE 2 FALSE 3 TRUE
In the above example, we have created a dataframe named dataframe1 with three columns Name
, Age
, Vote
.
Here,
dataframe[1]
- accesses all the elements of 1st column i.e.Name
dataframe[2]
- accesses all the elements of 3rd column i.e.Vote
Example 2: Use Column Name to Access Dataframe Column in R
# Create a data frame
dataframe1 <- data.frame (
Name = c("Juan", "Alcaraz", "Simantha"),
Age = c(22, 15, 19),
Vote = c(TRUE, FALSE, TRUE)
)
# access Name column
print(dataframe1[["Name"]])
# access Age column
print(dataframe1[["Age"]])
Output
[1] "Juan" "Alcaraz" "Simantha" [1] 22 15 19
In the above example, we have used the [[ ]]
operator to access columns of the dataframe named dataframe1.
Here,
dataframe[["Name"]]
- accesses all the elements of theName
column.dataframe[["Age"]]
- accesses all the elements of theAge
column.
Example 3: Use Column Name and $ to Access Column
# Create a data frame
dataframe1 <- data.frame (
Name = c("Juan", "Alcaraz", "Simantha"),
Age = c(22, 15, 19),
Vote = c(TRUE, FALSE, TRUE)
)
# access Age column
print(dataframe1$Age)
# access Vote column
print(dataframe1$Vote)
Output
[1] 22 15 19 [1] TRUE FALSE TRUE
In the above example, we have used the $
operator and column name to access columns of the dataframe1 dataframe.
Here,
dataframe$Age
- accesses all the elements of theAge
column.dataframe$Vote
- accesses all the elements of theVote
column.