[R] Existence of non-vectorised functions

[Ravi Varadhan]

Thanks to Uwe Ligges and Ben Bolker for their responses.  My main concern
was with the fact that R doesn't issue a warning when the user attempts an
"if" test with a vector argument.  Splus (at least Splus 6) does do this,
saying that only the first element is used in testing the condition. I feel
that R should also give this warning.

thanks again,
Ravi.

----- Original Message -----
From: "Uwe Ligges" <ligges at statistik.uni-dortmund.de>
To: "Ravi Varadhan" <rvaradha at jhsph.edu>
Cc: <r-help at stat.math.ethz.ch>
Sent: Tuesday, November 26, 2002 12:43 PM
Subject: Re: [R] Existence of non-vectorised functions


>
>
> Ravi Varadhan wrote:
> >
> > Dear R-Group:
> >
> > Recently, I ran into a problem.  I was using a function called "I.1",
> > which evaluates the first-order modified Bessel function of the first
> > kind, in the package "CircStats". This function is not vectorized,
> > since it uses a couple of "if" conditions.  However, when I called this
> > function with a vector argument, I got no error/warning messages in
> > R1.5.1 (under Windows 2000). Furthermore, the results were generally
> > incorect (please see the attached results).  However, if I vectorized
> > it using "ifelse" everything is fine (I created a function
> > called "myI.1" to do this).  I was wondering if there are functions in
> > other packages, where such problems exist due to non-vectorization?
>
> That's extremely probable. It depends on the package author and the
> complexity of the problem, thus you have to check it yourself whether it
> works vectorized or not, e.g. in the help files.
>
> BTW: You might want to send your improvements of I.1() to the package
> author as well (or even at first - hint, hint) ...
>
> Uwe Ligges
>
>
> > thanks,
> > Ravi.
> >
> > #######################################################
> > > require(CircStats)
> > > I.1(1:10)
> >  [1]    0.5651591    1.5906369    3.9533702    9.7594643   24.3351955
> >  [6]   61.3232698  155.7162813  396.4825232 1005.2747089 2517.6347571
> > > myI.1(1:10)
> >  [1]    0.5651591    1.5906369    3.9533702    9.7594652   24.3356418
> >  [6]   61.3419369  156.0390965  399.8731348 1030.9147087 2670.9883206
> >
>
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