[datatable-help] Access to local variables in "j" expressions

[Short, Tom]

I've got a fix for this. It'll probably be a couple of days before I can get it up to R-forge.

- Tom

> -----Original Message-----
> From: datatable-help-bounces at lists.r-forge.r-project.org 
> [mailto:datatable-help-bounces at lists.r-forge.r-project.org] 
> On Behalf Of Short, Tom
> Sent: Saturday, May 08, 2010 7:35 AM
> To: Johann Hibschman; datatable-help at lists.r-forge.r-project.org
> Subject: Re: [datatable-help] Access to local variables in 
> "j" expressions
> 
> I think it's a bug, Johann. I'll dig deeper. Thanks for reporting it.
> 
> - Tom
>  
> 
> > -----Original Message-----
> > From: datatable-help-bounces at lists.r-forge.r-project.org
> > [mailto:datatable-help-bounces at lists.r-forge.r-project.org]
> > On Behalf Of Johann Hibschman
> > Sent: Friday, May 07, 2010 4:53 PM
> > To: datatable-help at lists.r-forge.r-project.org
> > Subject: [datatable-help] Access to local variables in "j" 
> expressions
> > 
> > I'm just taking a look at data.table again, now that 1.4.1 has been 
> > released. I tried the following:
> > 
> >   dt.test <- data.table(n=c("a","a","b"), x=1:3, key="n")
> > 
> >   global.sum7 <- function (y) {
> >    sum(y) + 7
> >   }
> > 
> >   test.1 <- function (dt) {
> >    local.sum7 <- global.sum7
> >    dt[, list(out=local.sum7(x)), by=n]
> >   }
> > 
> >   test.1(dt.test)
> > 
> >  This failed, with 'Error in eval(expr, envir, enclos) : 
> > could not find function "local.sum7"'. Looking at the 
> documentation, I 
> > see:
> > 
> >      The j expression 'sees' variables in the calling frame 
> and above
> >      including .GlobalEnv, see the examples. This is base R
> >      functionality from eval() and with().
> > 
> > That led me to think that the above would work. Is this a 
> bug, or am I 
> > not understanding something?
> > 
> > Thanks,
> > Johann
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