[datatable-help] unique.data.frame should create a copy, right?

[Steve Lianoglou]

Last update here :-)

After more hemming and hawing, I've changed the name of the new
parameter added to duplicated.data.table and unique.data.table from
`by.columnss` to just `by`, as it (more or less) is the same idea as
the `by` in dt[x, i,j,by,...]

Sorry for any inconveniences caused if you've been working off of the
development version.

-steve


On Thu, Aug 15, 2013 at 9:35 PM, Ricardo Saporta
<saporta at scarletmail.rutgers.edu> wrote:
> Steve, great stuff!!
> thanks for making that happen
>
> Rick
>
>
> On Wed, Aug 14, 2013 at 8:30 PM, Steve Lianoglou
> <mailinglist.honeypot at gmail.com> wrote:
>>
>> Hi all,
>>
>> As I needed this sooner than I had expected, I just committed this
>> change. It's in svn revision 889.
>>
>> I chose 'by.columns' as the parameter names -- seemed to make more
>> sense to me, and using the short hand interactively saves a letter,
>> eg: unique(dt, by=c('some', 'columns')) ;-)
>>
>> Here's the note from the NEWS file:
>>
>> o  "Uniqueness" tests can now specify arbirtray combinations of
>> columns to use to test for duplicates. `by.columns` parameter added to
>> unique.data.table and duplicated.data.table. This allows the user to
>> test for uniqueness using any combination of columns in the
>> data.table, where previously the user only had the option to use the
>> keyed columns (if keyed) or all columns (if not). The default behavior
>> sets `by.columns=key(dt)` to maintain backward compatability. See
>> man/duplicated.Rd and tests 986:991 for more information. Thanks to
>> Arunkumar Srinivasan, Ricardo Saporta, and Frank Erickson for useful
>> discussions.
>>
>> Should work as advertised assuming my unit tests weren't too simplistic.
>>
>> Cheers,
>>
>> -steve
>>
>>
>>
>>
>> On Tue, Aug 13, 2013 at 1:24 PM, Steve Lianoglou
>> <mailinglist.honeypot at gmail.com> wrote:
>> > Thanks for the suggestions, folks.
>> >
>> > Matthew: do you have a preference?
>> >
>> > -steve
>> >
>> > On Mon, Aug 12, 2013 at 11:12 AM, Ricardo Saporta
>> > <saporta at scarletmail.rutgers.edu> wrote:
>> >> Steve,
>> >>
>> >> I like your suggestion a lot.  I can see putting column specification
>> >> to
>> >> good use.
>> >>
>> >> As for the argument name, perhaps
>> >>    'use.columns'
>> >>
>> >> And where a value of NULL or FALSE will yield same results as
>> >> `unique.data.frame`
>> >>
>> >>     use.columns=key(x)   # default behavior
>> >>     use.columns=c("col1name", "col7name")   #etc
>> >>     use.columns=NULL
>> >>
>> >>
>> >> Thanks as always,
>> >> Rick
>> >>
>> >>
>> >>
>> >> On Mon, Aug 12, 2013 at 1:51 PM, Steve Lianoglou
>> >> <mailinglist.honeypot at gmail.com> wrote:
>> >>>
>> >>> Hi folks,
>> >>>
>> >>> I actually want to revisit the fix I made here.
>> >>>
>> >>> Instead of having `use.key` in the signature to unique.data.table (and
>> >>> duplicated.data.table) to be:
>> >>>
>> >>> function(x,
>> >>>              incomparables=FALSE,
>> >>>              tolerance=.Machine$double.eps ^ 0.5,
>> >>>              use.key=TRUE, ...)
>> >>>
>> >>> How about we switch out use.key for a parameter that specifies the
>> >>> column names to use in the uniqueness check, which defaults to key(x)
>> >>> to keep backwards compatibility.
>> >>>
>> >>> For argument's sake (like that?), lets call this parameter `columns`
>> >>> (by.columns? with.columns? whatever) so:
>> >>>
>> >>> function(x,
>> >>>              incomparables=FALSE,
>> >>>              tolerance=.Machine$double.eps ^ 0.5,
>> >>>              columns=key(x), ...)
>> >>>
>> >>> Then:
>> >>>
>> >>> (1) leaving it alone is the backward compatibile behavior;
>> >>> (2) Perhaps setting it to NULL will use all columns, and make it
>> >>> equivalent to unique.data.frame (also the same when x has no key); and
>> >>> (3) setting it to any other combo of columns uses those columns as the
>> >>> uniqueness key and filters the rows (only) out of x accordingly.
>> >>>
>> >>> What do you folks think? Personally I think this is better on all
>> >>> accounts then just specifying to use the key or not and the only
>> >>> question in my mind is the name of the argument -- happy to hear other
>> >>> world views, however, so don't be shy.
>> >>>
>> >>> Thanks,
>> >>> -steve
>> >>>
>> >>> --
>> >>> Steve Lianoglou
>> >>> Computational Biologist
>> >>> Bioinformatics and Computational Biology
>> >>> Genentech
>> >>
>> >>
>> >
>> >
>> >
>> > --
>> > Steve Lianoglou
>> > Computational Biologist
>> > Bioinformatics and Computational Biology
>> > Genentech
>>
>>
>>
>> --
>> Steve Lianoglou
>> Computational Biologist
>> Bioinformatics and Computational Biology
>> Genentech
>
>



-- 
Steve Lianoglou
Computational Biologist
Bioinformatics and Computational Biology
Genentech