Re: [R] Error with function lda in package MASS (dimnames not equal?)

From: Joshua Gilbert <joshuacgilbert_at_gmail.com>
Date: Sun 12 Jun 2005 - 09:56:51 EST

I fully understand that this is a volunteer project, I'm a Debian user (not a developer... yet).

I have read the posting guide, but I forgot the protocol. First offence, won't happen again.

Thanks.

On 6/11/05, Prof Brian Ripley <ripley@stats.ox.ac.uk> wrote:
> The code will be changed to give a more informative error message in a
> future release. However, do remember that this is volunteer code, and it
> is not reasonable to expect volunteers to anticipate that a user will
> apply it in extremely unlikely circumstances.
>
> If you have a suggestion about code in a contributed package, please send
> it to the package maintainer (as the posting guide asks).
>
> On Sat, 11 Jun 2005, Joshua Gilbert wrote:
>
> > This is true, they are equal. I hadn't noticed that. Thank you.
> >
> > Now, if lda fails on this given input (equal means), shouldn't we
> > catch it and give a slightly better error message? I've spent a good
> > while going through the debugging process with lda.default. From that
> > perspective it appears that there is a simple change to remove the
> > problem. I am not saying that it is correct in any shape or form, but
> > there is a point where a single transpose would silence the error.
> >
> > So, from a usability standpoint, could we add a check for equal means
> > between classes and throw an error for that specific condition? Yes,
> > the user should not do that. But users may become more interested in
> > making the code run than checking on whether it's doing anything sane.
> >
> > If this isn't the place to do so, tell me. But, I'd like to petition
> > to alter the code of lda.default.
> >
> > On 6/10/05, Prof Brian Ripley <ripley@stats.ox.ac.uk> wrote:
> >> lda.default <- MASS:::lda.default and proceed.
> >>
> >> Look at the group means of your data: they are identical to machine
> >> accuracy.
> >>
> >> The question has to be `why are you trying to use lda to separate
> >> two groups with identical means'? Lda is not protected against that
> >> and it is rather unlikely unless you failed to inspect your data in any
> >> way.
> >>
> >> On Fri, 10 Jun 2005, Joshua Gilbert wrote:
> >>
> >>> This question appears to have been asked previously, but not answered.
> >>> the last response I can find to this previous thread is here:
> >>> http://tolstoy.newcastle.edu.au/R/help/04/07/0126.html. The asnwer was
> >>> to provide debugging info, not an answer.
> >>>
> >>> So the problem is that I'm trying to use lda on my dataset. You can
> >>> download my data here:
> >>> http://northstar-www.dartmouth.edu/~jgilbert/nolda, I used R's save
> >>> function to save objects data and classes (yes, I realize that I name
> >>> stomped the data function in package utils). To replicate my results,
> >>> simply enter the following:
> >>>> library(MASS)
> >>>> load('nolda')
> >>>> lda(data,classes)
> >>> Error in lda.default(x, grouping, ...) : length of 'dimnames' [2] not
> >>> equal to array extent
> >>>
> >>> Now, I don't know what that means.
> >>>> dimnames(data)
> >>> NULL
> >>>> dimnames(classes)
> >>> NULL
> >>>
> >>> As for debugging, I don't know how. I cannot debug lda.default as I
> >>> get the following:
> >>>> debug(lda.default)
> >>> Error: Object "lda.default" not found
> >>>
> >>> I think that that's pretty much it. Can anyone help me?
> >>>
> >>> ______________________________________________
> >>> R-help@stat.math.ethz.ch mailing list
> >>> https://stat.ethz.ch/mailman/listinfo/r-help
> >>> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
> >>>
> >>
> >> --
> >> 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
> >>
> >
> >
>
> --
> 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
>



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jun 12 10:03:42 2005

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