[R] remove 0 rows from a data frame

[Jason Turner]

Tord Snall wrote:

> Dear all,
> 
> As part of a larger function, I am randomly removing rows from a data
> frame. The number of removed rows is determmined by a Poisson distribution
> with a low mean. Sometimes, the random number is 0, and that's when the
> problem starts:
...
> However, sometimes rpois(1, 2) lead to nft=0, and in that case I do not want 
> 
> 
>>temp2<- temp[-sample(nrow(temp), 0), ]
>>temp2
> 
> [1] occ x   y   dbh age
> <0 rows> (or 0-length row.names)

This is a language feature, not a bug.  The easiest way around it is to 
catch the case where it's an issue.  Something like

if(nft==0) {
	rows <- 1:nrow(temp)
} else {
	rows <- -1 * sample(1:nrow(temp),nft)
}
temp2 <- temp[rows,]

Cheers

Jason
-- 
Indigo Industrial Controls Ltd.
http://www.indigoindustrial.co.nz
64-21-343-545
jasont at indigoindustrial.co.nz