[datatable-help] Output when using mean() with na.rm

[Matthew Dowle]

For the archives to close this thread, this bug is fixed in v1.6.1 now
on CRAN. The workaround should no longer be required. Thanks to Alex for
reporting it.
Matthew

On Thu, 2011-06-09 at 18:28 +0100, Matthew Dowle wrote:
> Interesting.   See FAQ 3.1, first bullet, for background on why it's doing 
> all.vars(jsub).
> 
> TRUE is a reserved word in R, so isn't considered a variable. T is a 
> variable (an object) in base holding the value TRUE (and may be masked by 
> user which is why T isn't recommended).
> 
> That leads to the more general bug :
> 
> > myvar = 6
> > table2[A=="b",B*myvar]
> Error in `[.data.table`(x, irows, all.vars(jsub), with = FALSE) :
>   undefined columns selected
> 
> It's just (I think) when i is integer or logical, and j uses a variable in 
> calling scope.  When i is data.table, should be fine.
> 
> A workaround in the meantime is :
> 
> table2[A=="b",mean(B,na.rm=get("T"))]
> 
> Bug #1421 now raised, thanks :
> 
> https://r-forge.r-project.org/tracker/index.php?func=detail&aid=1421&group_id=240&atid=975
> 
> Matthew
> 
> 
> 
> "Alexander Peterhansl" <APeterhansl at GAINCapital.com> wrote in message 
> news:FD59D3740610AB4388AA1BDC7FC9531D7971F8 at CRP11EXHMBS01.GAINCapital.com...
> 
> Dear Data Table Help List,
> 
> I am using data.table version 1.6 (with R version 2.13.0, 64-bit on Windows 
> 7) and I've come across some strange behavior.
> 
> Please look at the following example, where I simply take the mean of two 
> numbers.
> 
> > table1 <- data.table(A=c("a","b","b"),B=c(4,5,NA))
> > setkey(table1,A)
> > table1["b",mean(B,na.rm=T)]
>      A V1
> [1,] b  5
> # EXPECTED OUTPUT
> 
> > table2 <- data.table(A=c("a","b","b"),B=c(4,5,NA))
> > table2[A=="b",mean(B,na.rm=TRUE)]
> [1] 5
> # LESS EFFICIENT, BUT EXPECTED OUTPUT
> 
> > table2[A=="b",mean(B,na.rm=T)]
> Error in `[.data.table`(x, irows, all.vars(jsub), with = FALSE) :
>   undefined columns selected
> # WHY THE ERROR?
> 
> Any help would be much appreciated.
> 
> Regards,
> Alex
> 
> 
> 
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