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

[Peter Dalgaard]

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).
>   
df[!duplicated(df[,c("a","c")]),]

or perhaps

df[!duplicated(df[-2]),]
> 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
>>
>>     
>
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