dplyr: “Error in n(): function should not be called directly”

Question

I am attempting to reproduce one of the examples in the dplyr package but this error message. I am expecting to see a new column n produced with the frequency of each combination. Can someone tell me what I am missing? I triple-checked that the package was loaded. Thanks for the help, as always.

 library(dplyr)

# summarise peels off a single layer of grouping

by_vs_am <- group_by(mtcars, vs, am)

by_vs <- summarise(by_vs_am, n = n())

Error in n() : This function should not be called directly

Answer 1

You can try the following to remove this error:

• Make sure you load plyr first
• Both dplyr and plyr have the functions summarise/summarize. Look at the results of conflicts() to see masked objects.
• Use summarize with the package, something like this 

dplyr::summarize(count = n())

•  You can run this command to unload the plyr package.

detach("package:plyr", unload=TRUE) 

Then you can continue as expected.

library(dplyr) 

...

summarise(n = n())