[R] Filtering out a data.frame

Jeff08 jefferyding at gmail.com
Tue Jun 8 05:07:31 CEST 2010

Sample Data.Frame format

Name is Returns.nodup

            X       id ticker      date_ adjClose totret RankStk
427225 427225 00174410    AHS 2001-11-13    21.66    100    1235

"id" uniquely defines a row

What I am trying to do is filter out id's that have less than 1500 data
points (by date)

First, I used

total<-by(Returns.nodup, Returns.nodup$id,nrow)

which subsetted by ID and calculated the number of data points for each ID

Now I am trying to figure out a way to use this to filter out the original
data.frame (Returns.nodup)

I have tried using the following, but it is VERY slow:

z<-unlist(lapply(1:length(y), function(i) which(a$id==y[i]) ))

Is there a faster way to do this?

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