# Re: [R] Applying a function to each element of an array

From: Berton Gunter <gunter.berton_at_gene.com>
Date: Sat 08 Oct 2005 - 06:12:42 EST

Oops -- quite right, Brian. Interesting, as I stared at it for some time.

Sigh... now what **WAS** I looking for in the refrigerator?

• Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA

> -----Original Message-----
> From: Prof Brian Ripley [mailto:ripley@stats.ox.ac.uk]
> Sent: Friday, October 07, 2005 12:36 PM
> To: Berton Gunter
> Cc: 'Tim Smith'
> Subject: Re: [R] Applying a function to each element of an array
>
> On Fri, 7 Oct 2005, Berton Gunter wrote:
>
> > Well, since Sum(i=1 to i-n) =n*(n+1)/2, your loop simply gives
> > 1/4*count*(count-1).
> > So if your matrix is A, A*(A-1)/4 is about the quickest way
> to get your
>
> I think Bert has read ^ as *.
>
> >
> > -- Bert Gunter
> > Genentech Non-Clinical Statistics
> > South San Francisco, CA
> >
> > "The business of the statistician is to catalyze the
> scientific learning
> > process." - George E. P. Box
> >
> >
> >
> >> -----Original Message-----
> >> From: r-help-bounces@stat.math.ethz.ch
> >> [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Tim Smith
> >> Sent: Friday, October 07, 2005 11:48 AM
> >> To: r-help@stat.math.ethz.ch
> >> Subject: [R] Applying a function to each element of an array
> >>
> >> Hi,
> >>
> >> I have a 7000x7000 matrix, and each element is an integer.
> >> For each element, I want to apply the function :
> >>
> >> wt <- 0
> >> for(q in 1:count){
> >> wt <- wt + 0.5^(q-1)
> >> }
> >>
> >> I get the value of 'count' from the elements in the matrix ,
> >> and want to store the corresponding 'wt' value for that element.
> >>
> >> I suppose I could loop through the matrix, and apply the
> >> function to each element but this would take a really really
> >> long time. Are there any quicker ways to get the same result?
> >>
> >> many thanks,
> >>
> >> Tim
> >>
> >>
> >> ---------------------------------
> >>
> >>
> >> [[alternative HTML version deleted]]
> >>
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> >>
> >
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>
> --
> Brian D. Ripley, ripley@stats.ox.ac.uk
> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
> University of Oxford, Tel: +44 1865 272861 (self)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595
>

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