Re: [R] how to not sort factors when plotting

From: Lydia N. Slobodian <lns_at_cantab.net>
Date: Mon, 12 May 2008 17:53:10 +0100

Thanks for all of the help! Everything's working beautifully now, and I've accomplished in a few hours what it takes most of my colleagues weeks to do, so I think I'll stick with R after all!

Lydia

On Mon, May 12, 2008 at 4:41 PM, Jorge Ivan Velez <jorgeivanvelez_at_gmail.com> wrote:
>
>
> Hi Lydia,
>
> I compared my ratio function with Dimitris and Phil's suggestions. Please do
> NOT use my approach because it's painfully slow for a large vector (as Phil
> told me). Here is why (using Win XP SP2, Intel Core- 2 Duo 2.4 GHz, R 2.7.0
> Patched):
>
>
> # Vector
> x=rnorm(100000,0,1)
>
> # Suggestion
> new.ratio=function(x) x[2:length(x)]/x[1:(length(x)-1)]
>
> # My horrible function
> my.ratio=function(x){
>
> temp=NULL
> for (n in 1:length(x)) temp=c(temp,x[n]/x[n-1])
> temp
> }
>
> # System time
> t=system.time(my.ratio(x))
> tnr=system.time(new.ratio(x))
> t
> user system elapsed
> 38.79 0.06 39.31
> tnr
> user system elapsed
> 0 0 0
>
>
> Thanks to all,
>
> Jorge
>
>
>
> On Mon, May 12, 2008 at 11:15 AM, Phil Spector <spector_at_stat.berkeley.edu>
> wrote:
> > Another alternative would be to take advantage of R's vectorization:
> >
> >
> > >
> > >
> > > x=c(1,2,3,2,1,2,3)
> > > x[2:length(x)]/x[1:(length(x)-1)]
> > >
> >
> >
> > [1] 2.0000000 1.5000000 0.6666667 0.5000000 2.0000000 1.5000000
> >
> > The solution using your ratio function will be painfully slow
> > for a large vector.
> >
> > - Phil Spector
> > Statistical Computing Facility
> > Department of Statistics
> > UC Berkeley
> > spector_at_stat.berkeley.edu
> >
> >
>



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