diff(test$Y)/(test$Y)[-1] calculates (Y(t)-Y(t-1))/Y(t). To get (Y(t)-Y(t-1))/Y(t-1) instead, use diff(test$Y)/(test$Y)[-length(test$Y)] or better diff(test[,"Y"])/test[-nrow(test), "Y"]
-----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Yanyuan Zhu Sent: Mittwoch, 19. Juni 2013 13:04 To: r-help@r-project.org Subject: [R] how to get growth rate of a (time series) data? Hello all, now I'm trying to switch from Excel to R to deal with the data, and as a newbie i got the problem as follows. suppose I have a data named "test" test<- data.frame(year=c(1996:2011), Y=c(74163.6,81658.5,86531.6,91125.0,98749.0,109028.0,120475.6,136613.4,1 60956.6,187423.5,222712.5,266599.2,315974.6,348775.1,402816.5,465731.3)) in which Y means the GDP of a country If i want to get Delta Y = Y(t)-Y(t-1) , i could use diff() in R diff(test$Y) but what if i want to get gY=(Y(t)-Y(t-1))/Y(t-1)? seems diff(test$Y)/(test$Y)[-1] doesnt work ... thanks in advance [[alternative HTML version deleted]] ______________________________________________ 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. ______________________________________________ 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.
