On 09-07-2011, at 19:12, Luca Meyer wrote:
Thanks Jeff,
I have extracted the first 50 lines of the d4 data.frame and put them into the attached d4a.RData file. In case the list handler does not allow attachments I have uploaded a copy of the file onto my web site and it can be downloaded from: http://www.lucameyer.com/d4a.RData
Please notice that what I am trying to do is to aggregate over d4a$progetto and get a sum of d4a$ore. The error I get states:
Error in units == units[1L] : comparison between these types has not been implemented
Can you or anyone on the list spot what the matter could be for me?
By trial and error
aggregate(as.numeric(d4a$ore),list(d4a$progetto),sum)
Berend