One error you may encounter in R is:

Error in ifelse(df$team == "B", "Boston") : 
  argument "no" is missing, with no default

This error occurs when you use the ifelse() function in R but forget to include a third argument to specify the value that should be returned if the logical test returns false.

This tutorial shares exactly how to fix this error.

How to Reproduce the Error

Suppose we have the following data frame in R:

#create data frame
df <- data.frame(team=c('B', 'B', 'B', 'B', 'C', 'C', 'C', 'D'),
                 points=c(12, 22, 35, 34, 20, 28, 30, 18),
                 assists=c(4, 10, 11, 12, 12, 8, 6, 10))

#view data frame
df

  team points assists
1    B     12       4
2    B     22      10
3    B     35      11
4    B     34      12
5    C     20      12
6    C     28       8
7    C     30       6
8    D     18      10

Now suppose we attempt to use the ifelse() function to create a new column called city that contains “Boston” if the value in the team column is equal to “B”:

#attempt to create new column with team city
df$city <- ifelse(df$team=='B', 'Boston')

Error in ifelse(df$team == "B", "Boston") : 
  argument "no" is missing, with no default

We receive an error because we failed to provide a third argument in the ifelse() function that specifies the value we should return if the value in the team column is not equal to “B”.

How to Fix the Error

The way to fix this error is to simply provide a third argument in the ifelse() function that specifies the value we should return if the value in the team column is not equal to “B”.

The following syntax shows how to do so:

#create new column with team city
df$city <- ifelse(df$team=='B', 'Boston', 'Other')

#view updated data frame
df

  team points assists   city
1    B     12       4 Boston
2    B     22      10 Boston
3    B     35      11 Boston
4    B     34      12 Boston
5    C     20      12  Other
6    C     28       8  Other
7    C     30       6  Other
8    D     18      10  Other

Notice that we don’t receive  any error this time since we provided a third argument to the ifelse() function.

In this example, the ifelse() function returns a value of “Boston” if the value in the team column is equal to “B” or a value of “Other” if the value in the team column is anything else.