There is a general rule that scalar operations (that is functions
that work element-by-element and return a scalar result) preserve
attributes including names, dims and dimnames.
Similarly, there is a general rule about binary operations and attributes.
These things should definitely be in the `R Language Definition', but that
languishes as a draft. I am writing up comments on R internals (currently
an appendix on `Writing R Extensions', and this will go there (the section
on attributes is current work).
On Sat, 15 Jul 2006, François Pinard wrote:
> Hi, people.
>
> I was a bit intrigued by the message quoted below. Indeed, if pt() is
> given a matrix, it returns a matrix. Should this feature be documented?
> ?pt speaks about "a vector of quantiles", and says nothing about the
> type of what it returns.
>
> The same might presumably apply to other distribution-related functions.
>
> ----- Forwarded message from Martyn Plummer <[EMAIL PROTECTED]> -----
>
> From: Martyn Plummer <[EMAIL PROTECTED]>
> Date: Thu Apr 10 10:07:01 2003
> Subject: [R] for loops and counters
>
> Peter,
>
> You didn't say what goes wrong, but you mind find this version more useful
>
> tstat <- (matrix(means, k,k, byrow=TRUE) - matrix(means, k,k,byrow=FALSE))/rms
> pvalue <- 2*(1-pt(abs(tstat), df=df))
> pvalue[upper.tri(pvalue)]
>
> S is designed to allow you to work with "whole objects", which means that
> for loops can (and should) be avoided.
>
> Martyn
>
> On 05-Oct-99 Peter B. Mandeville wrote:
> > I am trying to assign values to a vector (pvalue). Similar code works in C
> > but not in R. What am I doing wrong?
>
> > r <- pvalue <- 0
> > for(i in (1:(k-1))){
> > for(j in (i+1):k){
> > r <- r+1
> > tstat <- (means[i]-means[j])/rms
> > pvalue[r] <- 2*(1-pt(abs(tstat),df))
> > }
> > }
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>
>
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
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