[R] using the function unique(), but asking it to ignore a column of a data.frame

[Prof Brian Ripley]

On Mon, 9 Jul 2007, Andrew Yee wrote:

> Thanks.  But in this specific case, I would like the output to include
> all three columns, including the "ignored" column (in this case, I'd
> like it to ignore column a).

sample.data.frame[!duplicated(sample.data.frame[-1]), ]

(index to exclude columns as you wish).

> Thanks,
> Andrew
>
> On 7/9/07, hadley wickham <h.wickham at gmail.com> wrote:
>> On 7/9/07, Andrew Yee <yee at post.harvard.edu> wrote:
>>> Take for example the following data.frame:
>>>
>>> a<-c(1,1,5)
>>> b<-c(3,2,3)
>>> c<-c(5,1,5)
>>> sample.data.frame<-data.frame(a=a,b=b,c=c)
>>>
>>> I'd like to be able to use unique(sample.data.frame), but have
>>> unique() ignore column a when determining the unique elements.
>>>
>>> However, I figured that this would be setting for incomparables=, but
>>> it appears that this funcationality hasn't been incorporated.  Is
>>> there a work around for this, i.e. to be able to get unique to only
>>> look at selected columns of a data frame?
>>
>> unique(df[,c("a","c")]) ?
>>
>> Hadley
>>
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595