You can use the following methods to get the column names of a data frame in R:
Method 1: Get All Column Names
colnames(df)
Method 2: Get Column Names in Alphabetical Order
sort(colnames(df))
Method 3: Get Column Names with Specific Data Type
colnames(df[,sapply(df,is.numeric)])
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', 'F'), points=c(18, 22, 19, 14, 14, 11), assists=c(5, 7, 7, 9, 12, 9), playoffs=c(TRUE, FALSE, FALSE, TRUE, TRUE, TRUE)) #view data frame df team points assists playoffs 1 A 18 5 TRUE 2 B 22 7 FALSE 3 C 19 7 FALSE 4 D 14 9 TRUE 5 E 14 12 TRUE 6 F 11 9 TRUE
Example 1: Get All Column Names
The easiest way to get all of the column names in a data frame in R is to use colnames() as follows:
#get all column names
colnames(df)
[1] "team" "points" "assists" "playoffs"
The result is a vector that contains all four column names from the data frame.
Example 2: Get Column Names in Alphabetical Order
To get the column names in a data frame in alphabetical order, you can use the sort() function as follows:
#get column names in alphabetical order
sort(colnames(df))
[1] "assists" "playoffs" "points" "team"
The result is a vector that contains all four column names from the data frame listed in alphabetical order.
You can also use the argument decreasing=TRUE to get the column names in reverse alphabetical order:
#get column names in reverse alphabetical order
sort(colnames(df), decreasing=TRUE)
[1] "team" "points" "playoffs" "assists"
Example 3: Get Column Names with Specific Data Type
You can use the following syntax to view the data type of each column in the DataFrame:
#view data type of each column
str(df)
'data.frame': 6 obs. of 4 variables:
$ team : chr "A" "B" "C" "D" ...
$ points : num 18 22 19 14 14 11
$ assists : num 5 7 7 9 12 9
$ playoffs: logi TRUE FALSE FALSE TRUE TRUE TRUEt
You can then use the sapply() function to only get the column names with a specific data type.
For example, we can use the following syntax to only get the column names that have a data type of numeric:
#get all columns that have data type of numeric
colnames(df[,sapply(df,is.numeric)])
[1] "points" "assists"
The result is a vector of column names that have a data type of numeric.
Additional Resources
The following tutorials explain how to perform other common operations in R:
How to Add Suffix to Column Names in R
How to Loop Through Column Names in R
How to Merge Data Frames by Column Names in R
