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How to Fix: Error in select unused arguments in R

In this tutorial, we will cover how to fix the error in selecting unused arguments in R. Error looks like below in R.

Error in select(., Species, Sepal.Length) : unused arguments (Species, Sepal.Length)

This error occurs when we try to use the select() function in R’s dplyr package, but we also have the some other R package which also has select() function. For example MASS package also has select() function. Since R has already loaded select() function from the MASS package which causes an error to appear.

How to reproduce the error

To recreate the error, follow the example below :

library(dplyr)
library(MASS)

iris %>%
select(Species, Sepal.Length) %>%
group_by(Species) %>%
summarize(mean_sepalLength = mean(Sepal.Length))

Error in select(., Species, Sepal.Length) : unused arguments (Species, Sepal.Length)

How to fix the error

By using this code dplyr::select( ) we have made sure select( ) function gets loaded from dplyr package instead of MASS package.

iris %>%
dplyr::select(Species, Sepal.Length) %>%
group_by(Species) %>%
summarize(mean_sepalLength = mean(Sepal.Length))

Output

# A tibble: 3 × 2
Species mean_sepalLength
1 setosa 5.01
2 versicolor 5.94
3 virginica 6.59

In the code above we used iris dataframe and calculated the average value of Sepal.Length variable by different types of Species.

Example 2

Let’s take one more example to understand it better. Here we are using mtcars dataframe. mpg refers to Miles/(US) gallon and cyl refers to Number of cylinders.

library(dplyr)
library(MASS)

mtcars %>%
select(cyl, mpg) %>%
group_by(cyl) %>%
summarize(mean_mpg = mean(mpg))

Error in select(., cyl, mpg) : unused arguments (cyl, mpg)

Solution

Similar to the previous example, we have used a double colon (::) to ask R to consider the select function from the dplyr package.

mtcars %>%
dplyr::select(cyl, mpg) %>%
group_by(cyl) %>%
summarize(mean_mpg = mean(mpg))

Output

# A tibble: 3 × 2
cyl mean_mpg

1 4 26.7
2 6 19.7
3 8 15.1

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