'Get dplyr count of distinct in a readable way

I'm new using dplyr, I need to calculate the distinct values in a group. Here's a table example:

data=data.frame(aa=c(1,2,3,4,NA), bb=c('a', 'b', 'a', 'c', 'c'))

I know I can do things like:

by_bb<-group_by(data, bb, add = TRUE)
summarise(by_bb, mean(aa, na.rm=TRUE), max(aa), sum(!is.na(aa)), length(aa))

But if I want the count of unique elements?

I can do:

  > summarise(by_bb,length(unique(unlist(aa))))

  bb length(unique(unlist(aa)))
1  a                          2
2  b                          1
3  c                          2

and if I want to exclude NAs I cand do:

> summarise(by_bb,length(unique(unlist(aa[!is.na(aa)]))))

  bb length(unique(unlist(aa[!is.na(aa)])))
1  a                                      2
2  b                                      1
3  c                                      1

But it's a little unreadable for me. Is there a better way to do this kind of summarization?

r dplyr

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'Get dplyr count of distinct in a readable way

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