[R] ?bug? strange factors produced by chron

[Prof Brian Ripley]

On Mon, 13 Feb 2006, Petr Pikal wrote:

> Thank you very much.
>
> On 13 Feb 2006 at 10:54, Prof Brian Ripley wrote:
>
> Date sent:      	Mon, 13 Feb 2006 10:54:21 +0000 (GMT)
> From:           	Prof Brian Ripley <ripley at stats.ox.ac.uk>
> To:             	Petr Pikal <petr.pikal at precheza.cz>
> Copies to:      	r-help at stat.math.ethz.ch
> Subject:        	Re: [R] ?bug? strange factors produced by chron
>
>> 1) The obvious test is via is.factor(), and you have not used that.
>
> I used it with TRUE result but did not use in my post (mea culpa)
>> is.factor(kvartaly)
> [1] TRUE
>
>> 2) Your example works for me, so what versions of R and chron is this?
>
> Package: chron
> Version: 2.3-1
> R 2.2.1 and W2000
>
> but problem is probably in interaction (see below)
>>
>> 3) Here's my guess. split is using the C-level test isFactor.  That
>> tests that the factor is of type integer, so please try
>>
>>>  typeof(kvartaly)
>
> > typeof(kvartaly)
> [1] "double"
>
> Problem is probably not in chron but in interaction, which silently
> transfers factor type to double
>
>> typeof(factor(letters[1:2]))
> [1] "integer"
>
>> typeof(interaction(factor(letters[1:2]), factor(letters[3:4])))
> [1] "double"

2.2.1 does not do that for me (and contains ans <- as.integer(ans), and 
has since Sept 2001).  Do you have a private copy?

-- 
Brian D. Ripley,                  ripley at 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