R help - Sep 2009 - Another Loop

Hello everyone,

Can somebody give a hint on how to go about speeding the following loop:

system.time(
for(i in 1:nrow(dat)){
if(dat$ycon[i]==0 || dat$ytrt[i]==0)
    dat$ycon[i]<-dat$ycon[i]+0.5
    dat$ytrt[i]<-dat$ytrt[i]+0.5
    dat$cony[i]<-dat$cony[i]+0.5
    dat$trty[i]<-dat$trty[i]+0.5
}
    )


-- 
-Tony

	[[alternative HTML version deleted]]

On Sep 29, 2009, at 5:53 PM, Antonio Paredes wrote:
> Hello everyone,
>
> Can somebody give a hint on how to go about speeding the following  
> loop:
>
You could try a loop-less approach:
> system.time(
>
targets <- dat$ycon[i]==0 | dat$ytrt[i]==0
>
>    dat$ycon[targets]<-dat$ycon[targets]+0.5
>    dat$ytrt[targets]<-dat$ytrt[targets]+0.5
>    dat$cony[targets]<-dat$cony[targets]+0.5
>    dat$trty[targets]<-dat$trty[targets]+0.5
>             )
>
>
David Winsemius, MD
Heritage Laboratories
West Hartford, CT