Dear R-user, a few weeks ago I consulted the list-serve with a similar question. However, my task changed a little but sufficiently to get lost again. So I would appreciate any help on the following issue.
I use the plm package and work with firm-level data in a panel. I would like to eliminate all firms that do not fulfill the requirement of having an observation in every variable used for at least x consecutive years. For illustration of the problem assume the following data set > data id year y z 1 a 2000 1 1 2 b 2000 NA 2 3 b 2001 3 3 4 c 1999 1 1 5 c 2000 2 2 6 c 2001 4 NA 7 c 2002 5 4 8 d 1998 6 5 9 d 1999 5 NA 10 d 2000 6 6 11 d 2001 7 7 12 d 2002 3 6 where id is the index of the firm, year the index for the year, and y and z are variables. Now, I would like to get rid of all firms with, let's say, less than 3 consecutive years in which there are observations for every variable. Hence, the procedure should yield > data.reduced id year y z 1 d 1998 6 5 2 d 1999 5 NA 3 d 2000 6 6 4 d 2001 7 7 5 d 2002 3 6 Thank you very much for any help! Cheers, Christian ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.