[datatable-help] 'by' on a numeric column produces inconsistent utput

[Arunkumar Srinivasan]

As I was just writing Kevin, I think (if @mnel could verify his output is correct), the reason is because Kevin's using R-devel... 

If you do the following shown below, then, `xx` should *not* have the same address as *dt$by* (as is the case for me). But for Kevin, they seem to be pointing to the same location and I can't figure out why it would/should, from how R has been working so far.
byval <- list(by=dt$by)
address(dt$by)
# [1] "0x7fa848ad8608"

address(byval)
# [1] "0x7fa84a93fa68"

xx = byval[[1L]]
address(xx)
# [1] "0x7fa848e3fc48"

address(list(xx))
[1] "0x7fa84aa1ba78"

data.table:::dradixorder(xx)
# [1] 2 3 1

byval
$by
[1] 0.7 0.4 0.4


Arun


On Thursday, December 19, 2013 at 9:36 AM, Arunkumar Srinivasan wrote:

> @mnel, I'm not sure I understand your output. Yours is different from the correct output, but it is also different from Kevin's. Basically, dt[, max(y), by=by] has no effect on yours and just returns back dt? 
> 
> Arun
> 
> 
> On Thursday, December 19, 2013 at 3:50 AM, Michael Nelson wrote:
> 
> > Using
> > data.table 1.8.11 (Fresh install from r-forge today)
> > R version 3.0.2 (2013-09-25)
> > Platform: x86_64-w64-mingw32/x64 (64-bit)
> > 
> > I get
> > 
> > by max
> > 1: 0.7 0.01464054
> > 2: 0.4 0.87328871
> > 3: 0.4 -1.02794620
> > 
> > On both runs.
> > 
> > 
> > 
> > 
> > ________________________________________
> > From: datatable-help-bounces at lists.r-forge.r-project.org (mailto:datatable-help-bounces at lists.r-forge.r-project.org) [datatable-help-bounces at lists.r-forge.r-project.org (mailto:datatable-help-bounces at lists.r-forge.r-project.org)] on behalf of Kevin Ushey [kevinushey at gmail.com (mailto:kevinushey at gmail.com)]
> > Sent: Thursday, 19 December 2013 12:54 PM
> > To: datatable-help at lists.r-forge.r-project.org (mailto:datatable-help at lists.r-forge.r-project.org)
> > Subject: [datatable-help] 'by' on a numeric column produces inconsistent output
> > 
> > I'm cross-posting this from the GitHub mirror:
> > https://github.com/arunsrinivasan/datatable/issues/2
> > 
> > For reference, I only see this with the latest RForge version of
> > data.table (1.8.11), not the CRAN version of data.table.
> > 
> > -----
> > 
> > library(data.table, lib="/Users/kevinushey/Library/R/3.1/library")
> > set.seed(32)
> > n <- 3
> > dt <- data.table(
> > y=rnorm(n),
> > by=round( rnorm(n), 1)
> > )
> > 
> > dt[,
> > list(max=max(y, na.rm=TRUE)),
> > by=list(by)
> > ]
> > 
> > dt[,
> > list(max=max(y, na.rm=TRUE)),
> > by=list(by)
> > ]
> > 
> > produces the output
> > 
> > > dt[,
> > + list(max=max(y, na.rm=TRUE)),
> > + by=list(by)
> > + ]
> > by max
> > 1: 0.4 0.01464054
> > 2: 0.4 0.87328871
> > 3: 0.7 -1.02794620
> > > 
> > > dt[,
> > + list(max=max(y, na.rm=TRUE)),
> > + by=list(by)
> > + ]
> > by max
> > 1: 0.4 0.8732887
> > 2: 0.7 -1.0279462
> > 
> > For some reason, the first return is wrong, while the second (and all
> > subsequent) output is correct. Any idea what's going on?
> > 
> > > sessionInfo()
> > R Under development (unstable) (2013-12-12 r64453)
> > Platform: x86_64-apple-darwin13.0.0 (64-bit)
> > 
> > locale:
> > [1] en_CA.UTF-8/en_CA.UTF-8/en_CA.UTF-8/C/en_CA.UTF-8/en_CA.UTF-8
> > 
> > attached base packages:
> > [1] stats graphics grDevices utils datasets methods base
> > 
> > other attached packages:
> > [1] data.table_1.8.11 knitr_1.5 devtools_1.4.1.99
> > BiocInstaller_1.13.3
> > 
> > loaded via a namespace (and not attached):
> > [1] compiler_3.1.0 digest_0.6.4 evaluate_0.5.1 formatR_0.10
> > httr_0.2 memoise_0.1
> > [7] parallel_3.1.0 plyr_1.8 RCurl_1.95-4.1 reshape2_1.2.2
> > stringr_0.6.2 tools_3.1.0
> > [13] whisker_0.3-2
> > 
> > ---
> > 
> > Kevin
> > _______________________________________________
> > datatable-help mailing list
> > datatable-help at lists.r-forge.r-project.org (mailto:datatable-help at lists.r-forge.r-project.org)
> > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
> > _______________________________________________
> > datatable-help mailing list
> > datatable-help at lists.r-forge.r-project.org (mailto:datatable-help at lists.r-forge.r-project.org)
> > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
> > 
> > 
> > 
> 
> 

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