R help - Jan 2005 - Array Manipulation

I have a data set that looks like the following:
ID  Responce
1   57
1   63
1   49
2   31
2   45
2   67
2   91
3   56
3   43
4   23
4   51
4   61
4   76
4   68
5   34
5   35
5   45
I used sample(unique(ID)) to select a sample if ID's, say, (1,4,5).  Now
I want to pull out the rows with ID's 1, 4, and 5.  I've tried forceing
the matrix into a vector but it does not create and appropriate vector.
 I've also tried the if statment but it didn't work right either.  Any
suggestions?

Something like:

dat[dat$ID %in% sample(unique(dat$ID), 3), ]

Andy
> From: cdsmith at ksu.edu
> 
> I have a data set that looks like the following:
> ID  Responce
> 1   57
> 1   63
> 1   49
> 2   31
> 2   45
> 2   67
> 2   91
> 3   56
> 3   43
> 4   23
> 4   51
> 4   61
> 4   76
> 4   68
> 5   34
> 5   35
> 5   45
> I used sample(unique(ID)) to select a sample if ID's, say, 
> (1,4,5).  Now
> I want to pull out the rows with ID's 1, 4, and 5.  I've 
> tried forceing
> the matrix into a vector but it does not create and 
> appropriate vector.
>  I've also tried the if statment but it didn't work right either. 
Any
> suggestions?
> 
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>

Liaw, Andy wrote:
> Something like:
> 
> dat[dat$ID %in% sample(unique(dat$ID), 3), ]
> 
or

subset(dat, ID %in% sample(unique(ID), 3))

which I find to be more readable.