tom soyer wrote: > Hi, > > I am trying to extract data from a ts object by month, e.g., extract Jan, > Feb, and Aug data from a monthly ts object. I tried the following but it > didn't work: > >> xa=1:50 >> ta=ts(xa,start=c(1990,1),frequency=12) >> ta[cycle(ta)==c(1,2)] # this method works but it's not what I want > [1] 1 2 13 14 25 26 37 38 49 50 >> ta[cycle(ta)==c(1,2,8)] # this method doesn't work, unfortunately > [1] 1 2 13 14 25 26 37 38 49 50 > Warning message: > In `==.default`(cycle(ta), c(1, 2, 8)) : > longer object length is not a multiple of shorter object length > > somehow ta[cycle(ta)==c(1,2)] works. But what I really need is for > ta[cycle(ta)==c(1,2,8)] to work, and it doesn't. Does anyone know how could > to do this kinds of data extraction? > > Thanks!
Tom, You need to use %in% when you want to test whether one or more values are in a second set of values. In this case: > ta[cycle(ta) %in% c(1, 2, 8)] [1] 1 2 8 13 14 20 25 26 32 37 38 44 49 50 BTW, the use of: > ta[cycle(ta) == c(1, 2)] [1] 1 2 13 14 25 26 37 38 49 50 results in a correct response, but largely by chance in this case because of the way in which the data is stored. You should be using: > ta[cycle(ta) %in% c(1, 2)] [1] 1 2 13 14 25 26 37 38 49 50 Note however, that if we use: > ta[cycle(ta) == c(1, 3)] [1] 1 13 25 37 49 we do not get the correct answer, which should be: > ta[cycle(ta) %in% c(1, 3)] [1] 1 3 13 15 25 27 37 39 49 See ?"%in%" for more information. HTH, Marc Schwartz ______________________________________________ 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.
