Perhaps it could read .I = 1:nrow(x). Note that .I does not equal 1:.N if there are groups.
On Tue, Apr 1, 2014 at 7:57 AM, Arunkumar Srinivasan <[email protected]> wrote: > The key part is "row locations in x". If it were to reset for each group, > then that part wouldn't have been necessary. > Perhaps it'd be clearer if it were something like this: ".I is an integer > vector which, for each group, holds the corresponding row numbers in/from/of > x"? Not sure which preposition is most appropriate here. > > Arun > > From: Gabor Grothendieck [email protected] > Reply: Gabor Grothendieck [email protected] > Date: April 1, 2014 at 1:45:39 PM > To: Arunkumar Srinivasan [email protected] > Cc: [email protected] > [email protected] > Subject: Re: [datatable-help] .I does not respect by > > From the documentation I would have expected that the row locations > start over at 1 for each group so that .I = 1:.N. but these are not > equivalent. > > On Tue, Apr 1, 2014 at 7:20 AM, Arunkumar Srinivasan > <[email protected]> wrote: >> Gabor, >> >> It's the same as in 1.8.10 and 1.9.2. What is contradicting in >> ?data.table? >> It says under .I: ".I is an integer vector length .N holding the row >> locations in x for this group." >> >> The row locations in x for b=1,2,1,2 are 1,2,3,4 which then becomes 1,3 >> and >> 2,4 for this group => b=1 and b=2 respectively. >> >> >> Arun >> >> From: Gabor Grothendieck [email protected] >> Reply: Gabor Grothendieck [email protected] >> Date: April 1, 2014 at 1:09:23 PM >> To: [email protected] >> [email protected] >> Subject: [datatable-help] .I does not respect by >> >> In the following .I seems not to be within group. >> >>> dt <- data.table(a = 1:4, b = 1:2) >>> dt[, .I, by = b] >> b .I >> 1: 1 1 >> 2: 1 3 >> 3: 2 2 >> 4: 2 4 >>> packageVersion("data.table") >> [1] '1.9.3' >> >> This seems contrary to ?data.table. >> >> >> -- >> Statistics & Software Consulting >> GKX Group, GKX Associates Inc. >> tel: 1-877-GKX-GROUP >> email: ggrothendieck at gmail.com >> _______________________________________________ >> datatable-help mailing list >> [email protected] >> >> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > > > > -- > Statistics & Software Consulting > GKX Group, GKX Associates Inc. > tel: 1-877-GKX-GROUP > email: ggrothendieck at gmail.com -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
