You can use the following basic syntax to select columns by index in R:

#select specific columns by index
df[ , c(1, 4)]

#select specific columns in index range
df[ , 1:3]

#exclude specific columns by index
df[ , -c(2, 5)]

The following examples show how to use this syntax in practice with the following data frame:

#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),
                 blocks=c(7, 7, 5, 9, 13))

#view data frame
df

  team points assists rebounds blocks
1    A     99      33       30      7
2    B     90      28       28      7
3    C     86      31       24      5
4    D     88      39       24      9
5    E     95      34       28     13

Example 1: Select Columns by Index

The following code shows how to select specific columns by index:

#select columns in 1st and 4th position
df[ , c(1, 4)]

  team rebounds
1    A       30
2    B       28
3    C       24
4    D       24
5    E       28

Example 2: Select Columns in Index Range

The following code shows how to select specific columns in an index range:

#select columns in positions 1 through 3df[ , 1:3]

  team points assists
1    A     99      33
2    B     90      28
3    C     86      31
4    D     88      39
5    E     95      34

Example 3: Exclude Columns by Index

The following code shows how to exclude specific columns by index:

#select all columns except columns in positions 2 and 5
df[ , -c(2, 5)]

  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 this returns all of the columns in the data frame except for the columns in index positions 2 and 5.

The following tutorials explain how to perform other common operations on data frame columns in R: