[R] as.integer question

[Erin Hodgess]

Thanks to all!

This is really helpful!

Sincerely,
Erin


On Jan 17, 2008 12:00 PM, Marc Schwartz <marc_schwartz at comcast.net> wrote:
> Erin Hodgess wrote:
> > Hi R People:
> >
> > I'm reading "Statistical Computing with R", by Maria Rizzo, and it's
> > really good.
> >
> > Anyhow, I have a question about something in there.
> >
> >> u<- runif(5)
> >> u
> > [1] 0.1177041 0.4271790 0.4601597 0.2204846 0.4051473
> >> #in the book
> >> sum(as.integer(u>  0.4))
> > [1] 3
> >> #what I would do
> >> sum(u>  0.4)
> > [1] 3
> >
> > Is one way better than the other, please?
> >
> > Thanks,
> > Erin
>
> There is additional coercion overhead in the first approach, since
> as.integer() is called separately:
>
> set.seed(1)
>
> Vec <- sample(c(TRUE, FALSE), 1000000, replace = TRUE)
>
>  > system.time(sum(Vec))
>    user  system elapsed
>   0.004   0.000   0.025
>
>  > system.time(sum(as.integer(Vec)))
>    user  system elapsed
>   0.013   0.019   0.050
>
>
> To paraphrase a financial quote: A microsecond here, a microsecond there
> and pretty soon you are talking about a serious amount of time...  ;-)
>
> HTH,
>
> Marc Schwartz
>
>



-- 
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodgess at gmail.com