You can use the following basic syntax to find the max value in each row of a data frame in R:

df$max <- apply(df, 1, max, na.rm=TRUE)

This particular syntax creates a new column called max that contains the max value in each row of the data frame.

The following example shows how to use this syntax in practice.

Example: Find the Max Value in Each Row in R

Suppose we have the following data frame in R:

#create data frame
df <- data.frame(points=c(4, NA, 10, 2, 15, NA, 7, 22),
                 rebounds=c(NA, 3, 9, 7, 6, 8, 14, 10),
                 assists=c(10, 9, 4, 4, 3, 7, 10, 11))

#view data frame
df

  points rebounds assists
1      4       NA      10
2     NA        3       9
3     10        9       4
4      2        7       4
5     15        6       3
6     NA        8       7
7      7       14      10
8     22       10      11

We can use the following syntax to create a new column called max that contains the max value in each row:

#add new column that contains max value in each row
df$max <- apply(df, 1, max, na.rm=TRUE)

#view updated data frame
df

  points rebounds assists max
1      4       NA      10  10
2     NA        3       9   9
3     10        9       4  10
4      2        7       4   7
5     15        6       3  15
6     NA        8       7   8
7      7       14      10  14
8     22       10      11  22

The new column called max contains the max value in each row.

Note: If you don’t include na.rm=TRUE within the apply() function, then NA values will be returned if they exist anywhere in the row.