R devel - Jun 2003 - mva:princomp.default not set correctly (PR#3168)

Full_Name: Andrew Irwin
Version: 1.7.0
OS: Win98
Submission from: (NULL) (165.230.175.97)



It is impossible to set both xlim and ylim in princomp or princomp.default.

For example
  data(USArrests)
  biplot(princomp(USArrests))
works fine, but
  biplot(princomp(USArrests), xlim=c(-0.4, 0.4), ylim=c(-0.5,0.4) )
does not do what I would expect -- the ylim gets ignored.

The offending bit of code from mva:princomp.default seems to be

    if (missing(xlim) && missing(ylim)) 
        xlim <- ylim <- rangx1 <- rangx2 <- range(rangx1, rangx2)
    else if (missing(xlim)) 
        xlim <- rangx1
    else ylim <- rangx2


This if .. else if .. else clause is not written the way I think it should be
written.  The else clause should only be executed if ylim is missing, but it
will be executed if xlim and ylim are both present.

Suggested rewrite:

    if (missing(xlim) && missing(ylim)) 
        xlim <- ylim <- rangx1 <- rangx2 <- range(rangx1, rangx2)
    else if (missing(xlim)) 
        xlim <- rangx1
    else if (missing(ylim))
        ylim <- rangx2

ifelse clause might be better, but less readable.

Cheers,

Andrew

This is not about princomp.default at all!  That snippet of code does not
appear there.

Please do check against the S-PLUS original of biplot.default: this is in
biplot.default.  I very much doubt if you understand the intentions
(not that I do either).

On Mon, 2 Jun 2003 irwin@imcs.rutgers.edu wrote:
> Full_Name: Andrew Irwin
> Version: 1.7.0
> OS: Win98
> Submission from: (NULL) (165.230.175.97)
> 
> 
> 
> It is impossible to set both xlim and ylim in princomp or princomp.default.
> 
> For example
>   data(USArrests)
>   biplot(princomp(USArrests))
> works fine, but
>   biplot(princomp(USArrests), xlim=c(-0.4, 0.4), ylim=c(-0.5,0.4) )
> does not do what I would expect -- the ylim gets ignored.
Since when were your expectations the determinant of a bug?
> The offending bit of code from mva:princomp.default seems to be
> 
>     if (missing(xlim) && missing(ylim)) 
>         xlim <- ylim <- rangx1 <- rangx2 <- range(rangx1,
rangx2)
>     else if (missing(xlim)) 
>         xlim <- rangx1
>     else ylim <- rangx2
> 
> 
> This if .. else if .. else clause is not written the way I think it should
be
> written.  The else clause should only be executed if ylim is missing, but
it
> will be executed if xlim and ylim are both present.
> 
> Suggested rewrite:
> 
>     if (missing(xlim) && missing(ylim)) 
>         xlim <- ylim <- rangx1 <- rangx2 <- range(rangx1,
rangx2)
>     else if (missing(xlim)) 
>         xlim <- rangx1
>     else if (missing(ylim))
>         ylim <- rangx2
> 
> ifelse clause might be better, but less readable.
> 
> Cheers,
> 
> Andrew
> 
> ______________________________________________
> R-devel@stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-devel
> 
-- 
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