[R] How to count rows with a condition

[David Winsemius]

On Oct 17, 2012, at 5:44 AM, fxen3k wrote:

> Hi,
>
> I have a dataset called "data". There is one row called "ac_name".  
> Some
> names in this column appear very often, some less.
> What I want is to filter this dataset with the following condition:
>
> Exclude the names, which appear more than five times. (example:  
> House A
> appears 8 times ==> exclude it; House B appears 5 times ==> include  
> it etc.)
>
> In the end, I want to have the old "data" dataset excluding the rows  
> with
> the above mentioned condition and another list with all the names  
> which have
> been excluded.
>

data[ ave(data$ac_name, data$ac_name, length) <= 5, ]  # all with 5 or  
fewer entries

-- 

David Winsemius, MD
Alameda, CA, USA