indexing question

	my.data.frame <- data.frame(a=rnorm(10),  
b=factor(sample(letters[1:4], 10, replace=T)))
	str(my.data.frame)
	my.data.frame[my.data.frame$b == "a", ]
	subset(my.data.frame, b == "a")

have a look at ?"[.data.frame"; what you need is the following:

dat <- data.frame(a = rbinom(20, 1, 0.5), x = rnorm(20), y =  
rnorm(20))

dat
dat[dat$a == 1, ]


I hope it helps.

Best,
Dimitris


Bunny, lautloscrew.com wrote:

Hi all,

i have a pretty easy indexing question, at least i believe so. The  
main
reason i post it here, is that brackets and $ are hard to google.

How do I index correctly, if i just want to display the whole dataset
conditioned on the fact that some particular column equals one.

I know i can do something like:   data$somecolumn[data$particularcol
==1] . That will show all "some column" values where the particular
column is 1.
Unfortunately something like : data[data$particularcol ==1] does not
work to get the whole matrix.

is there some easy way except the % in % stuff ?

Thx in advance

--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014