Thanks Barry for the code sample, and Thanks Duncan for the clarification. Both replies help a lot!
Best Regards, Xie Chao On Wed, Apr 21, 2010 at 2:50 AM, Barry Rowlingson <b.rowling...@lancaster.ac.uk> wrote: > On Tue, Apr 20, 2010 at 7:03 PM, Xie Chao <xiech...@gmail.com> wrote: >> Dear All, >> >> I am wondering is there any shift (or pop or push or unshift) equivalent in >> R? >> For example, >> shift(x) # should return x[1], and x becomes x[-1] >> > > I seem to have implemented a FIFO stack in 2003: > > http://finzi.psych.upenn.edu/R/Rhelp02/archive/15541.html > > but note the reply commenting on the existence of the "stack" > function in R which stacks data on top of other data. > > Here's sample usage once you've loaded the code from that old posting: > >> s=stack() >> push(s,1) >> s > [[1]] > [1] 1 > >> push(s,3) >> push(s,4) >> pop(s) > [1] 4 >> pop(s) > [1] 3 >> s > [[1]] > [1] 1 > > If you want to implement a 'shift' method, just look at the existing > pop and push methods and write something similar. Note how the > functions are created on the object, and then called from S3 methods. > Note the use of <<- within the functions on the object. There's > probably better ways to do this, and with S4 methods. > > Barry > > > > -- > blog: http://geospaced.blogspot.com/ > web: http://www.maths.lancs.ac.uk/~rowlings > web: http://www.rowlingson.com/ > twitter: http://twitter.com/geospacedman > pics: http://www.flickr.com/photos/spacedman > ______________________________________________ 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.
