[R] subsetting dataframe by rownames to be excluded

[Prof Brian Ripley]

On Sat, 11 Oct 2008, Alexy Khrabrov wrote:

> Is there a way to select a subset of a dataframe consisting of all those rows 
> with rownames *except* from a subset of rownames to be excluded?  Example:

Yes: DF[is.na(match(row.names(DF), exclude_me)), ]

>
>> a <- data.frame(x=1:10,y=10:1)
>> a <- a[order(a$y),] # to make rownames differ visually
>
>> a[8,]
> x y
> 3 3 8
>
>> a["8",]
> x y
> 8 8 3
>
>> a[-8,]
>   x  y
> 10 10  1
> 9   9  2
> 8   8  3
> 7   7  4
> 6   6  5
> 5   5  6
> 4   4  7
> 2   2  9
> 1   1 10
>
>> a[-"8",]
> Error in -"8" : invalid argument to unary operator
>
> -- is there a similar exclusion operator or simple way?  So far the best I 
> can do is
>
>> a[setdiff(rownames(a),"8"),]
>   x  y
> 10 10  1
> 9   9  2
> 7   7  4
> 6   6  5
> 5   5  6
> 4   4  7
> 3   3  8
> 2   2  9
> 1   1 10
>
> Cheers,
> Alexy

-- 
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)
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