use "split' to split your dataframe by country and then do the diff. On Sat, Sep 20, 2008 at 8:54 PM, Gabriel Paul Mihalache <[EMAIL PROTECTED]> wrote: > I was suggested that more details with help re: my question on first > differences in panel data... > The data set in question is PWT6.2: > >> str(pwt6.2) > 'data.frame': 10340 obs. of 27 variables: > $ country: Factor w/ 188 levels "Afghanistan",..: 1 1 1 1 1 1 1 1 1 1 ... > $ isocode: Factor w/ 188 levels "AFG","ALB","DZA",..: 1 1 1 1 1 1 1 1 1 1 ... > $ year : int 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 ... > $ pop : num 8150 8284 8425 8573 8728 ... > ... > $ cgdp : num NA NA NA NA NA NA NA NA NA NA ... > ... > $ grgdpch: num NA NA NA NA NA NA NA NA NA NA ... > > The panel has countries as units and years for time. > What I want to do is have a fist different of logs of cgdp and pop. > > The reason why I can't use diff(log(pop)) is because when the data for > a country ends, e.g. Afghanistan 2004, the next observation belongs to > another country, e.g. Albania 1950, and R will do a first log > difference between the population of Albania in 1950 and that of > Afghanistan in 2004, instead of NA (since I don't have data for > Albania 1949). > > I need a diff() that's aware of the panel structure of the data (i.e. > the countries). > The plm package does this, but only in a regression. I found no > function that I can use to save the log differences. > > Thank you for your time, > Gabriel > > ______________________________________________ > 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. >
-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ 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.
