[datatable-help] FR #5249 - rbindlist gains use.names and fill arguments

[Gabor Grothendieck]

Then why not make the default of use.names be fill. Then you don't get
the warning and you can tell just from the argument list what the
dependencies are.

On Tue, May 20, 2014 at 4:07 PM, Arunkumar Srinivasan
<aragorn168b at gmail.com> wrote:
> Hi Gabor,
>
> Thanks for the quick response. Just to be clear, you don’t have to set
> use.names=TRUE when fill=TRUE. If you just set fill=TRUE and use.names
> happens to be FALSE, then it’ll automatically set it to TRUE (with a
> message/warning), which you can safely ignore. Do you find this still ugly?
> You’ll get the warning if you use rbindlist with just fill=TRUE (because
> use.name=FALSE by default).
>
>
> Arun
>
> From: Gabor Grothendieck ggrothendieck at gmail.com
> Reply: Gabor Grothendieck ggrothendieck at gmail.com
> Date: May 20, 2014 at 10:04:21 PM
> To: Arunkumar Srinivasan aragorn168b at gmail.com
> Cc: datatable-help at lists.r-forge.r-project.org
> datatable-help at lists.r-forge.r-project.org
> Subject:  Re: [datatable-help] FR #5249 - rbindlist gains use.names and fill
> arguments
>
> The requirement to set use.names to TRUE if fill is TRUE seems ugly.
> I suggest that fill be the default for use.names.
>
> On Tue, May 20, 2014 at 3:27 PM, Arunkumar Srinivasan
> <aragorn168b at gmail.com> wrote:
>> Hello everyone,
>>
>> With the latest commit #1266, the extra functionality offered via rbind
>> (use.names and fill) is also now available to rbindlist. In addition, the
>> implementation is completely moved to C, and is therefore tremendously
>> fast,
>> especially for cases where one has to bind using with use.names=TRUE
>> and/or
>> with fill=TRUE. I’ll try to put out a benchmark comparing speed
>> differences
>> with the older implementation ASAP.
>>
>> Note that this change comes with a very low cost to the default speed to
>> rbindlist - with use.names=FALSE and fill=FALSE. As an example, binding
>> 10,000 data.tables with 20 columns each, resulted in the new version
>> running
>> in 0.107 seconds, where as the older version ran in 0.095 seconds.
>>
>> In addition the documentation for ?rbindlist also has been improved (#5158
>> from Alexander). Here’s the change log from NEWS:
>>
>> o 'rbindlist' gains 'use.names' and 'fill' arguments and is now
>> implemented entirely in C. Closes #5249
>> -> use.names by default is FALSE for backwards compatibility
>> (doesn't bind by names by default)
>> -> rbind(...) now just calls rbindlist() internally, except that
>> 'use.names' is TRUE by default,
>> for compatibility with base (and backwards compatibility).
>> -> fill by default is FALSE. If fill is TRUE, use.names has to be
>> TRUE.
>> -> At least one item of the input list has to have non-null column
>> names.
>> -> Duplicate columns are bound in the order of occurrence, like
>> base.
>> -> Attributes that might exist in individual items would be lost in
>> the bound result.
>> -> Columns are coerced to the highest SEXPTYPE, if they are
>> different, if/when possible.
>> -> And incredibly fast ;).
>> -> Documentation updated in much detail. Closes DR #5158.
>> Eddi's (excellent) work on finding factor levels, type coercion of
>> columns etc. are all retained.
>>
>> Please try it and write back if things aren’t working as it was before.
>> The
>> tests that had to be fixed are extremely rare cases. I suspect there
>> should
>> be minimal issue, if at all, in this version. However, I do find the
>> changes
>> here bring consistency to the function.
>>
>> One (very rare) feature that is not available due to this implementation
>> is
>> the ability to recycle.
>>
>> dt1 <- data.table(x=1:3, y=4:6, z=list(1:2, 1:3, 1:4))
>> lst1 <- list(x=4, y=5, z=as.list(1:3))
>>
>> rbind(dt1, lst1)
>> # x y z
>> # 1: 1 4 1,2
>> # 2: 2 5 1,2,3
>> # 3: 3 6 1,2,3,4
>> # 4: 4 5 1
>> # 5: 4 5 2
>> # 6: 4 5 3
>>
>> The 4,5 are recycled very nicely here.. This is not possible at the
>> moment.
>> This is because the earlier rbind implementation used as.data.table to
>> convert to data.table, however it takes a copy (very inefficient on huge /
>> many tables). I’d love to add this feature in C as well, as it would help
>> incredibly for use within [.data.table (now that we can fill columns and
>> bind by names faster). Will add a FR.
>>
>> In summary, I think there should be minimal issues, if any and should be
>> much faster (for rbind cases). Please write back what you think, if you
>> happen to try out.
>>
>>
>>
>> Arun
>>
>>
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>>
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>
>
>
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> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
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> email: ggrothendieck at gmail.com



-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com