[R] subsetting dataframe by rownames to be excluded

[Alexy Khrabrov]

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:

 > 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