[R] subsetting data set dimenion problem

[Clint Harshaw]

(See DAAG book, p. 173, ex. 3)

I'm a new user of R, and I'm following the DAAG text. I want to create a 
subset of the races2000 data frame, but get errors because of a mismatch 
of values in some columns:

 > library(DAAG)
 > attach(races2000)
 > hills2000 <- races2000[races2000$type == 'hill']
Error in as.matrix.data.frame(x) : dim<- : dims [product 770] do not 
match the length of object [771]

However, if I follow the solution given, and remove redundant columns 1 
through 6 and column 11 (which I won't need, since I know they are going 
to have the same value), I don't get the error:

 > hills2000 <- races2000[races2000$type == 'hill', -c(1:6,11)]
 > hills2000
                        dist climb      time      timef
Tiso Carnethy          6.00  2500 0.7822222  0.9191667
[...]
Cornalees              5.50   800 0.6183333         NA
[...]

What is causing the error with my original subsetting? I speculated it 
was related to the NA values, but there is an NA in the resulting 
hills2000, corresponding to the Cornalees hill race.

Thanks,
Clint
-- 
Clint Harshaw, PhD		
Department of Mathematics
Presbyterian College
Clinton SC  29325

EMail: charshaw at presby.edu	
Phone: 864.833.8995
Fax: 864.938.3769
Office: Harrington-Peachtree Rm 412