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.

#get column names in reverse alphabetical ordersort(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 columnstr(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 numericcolnames(df[,sapply(df,is.numeric)])

[1] "points"  "assists"

The result is a vector of column names that have a data type of numeric.