[R] List seems to drop empty levels of factors when containin g them

[Andrew Robinson]

Matt,

very astute - thanks.  I did indeed have Hmisc loaded.

Andrew

On Tue, Nov 09, 2004 at 08:12:57PM -0800, Austin, Matt wrote:
> I don't get the same result, do you have a package loaded that would change
> the default behavior (such as Hmisc)?
> 
> > list(grp.1)
> [[1]]
> [1] 1 2
> Levels: 1 2
> 
> > list(grp.1[mask])
> [[1]]
> [1] 1
> Levels: 1 2
> 
> > library(Hmisc)
> <<snip>>
> 
> > list(grp.1[mask])
> [[1]]
> [1] 1
> Levels: 1
> 
> --Matt
> 
> > version
>          _              
> platform i386-pc-mingw32
> arch     i386           
> os       mingw32        
> system   i386, mingw32  
> status                  
> major    2              
> minor    0.0            
> year     2004           
> month    10             
> day      04             
> language R             
> 
> 
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Andrew Robinson
> Sent: Tuesday, November 09, 2004 19:44 PM
> To: R-Help Discussion
> Cc: Andrew Robinson
> Subject: [R] List seems to drop empty levels of factors when containing
> them
> 
> 
> Greetings R community,
> 
> I am curious about the following behaviour: if I define a factor, and
> then store a subset of it in a list, the stored version seems to drop
> levels that were not included in the subset.  E.g. ..
> 
> > mask <- c(T, F)
> > grp.1 <- factor(c(1,2))
> > list(grp.1)
> [[1]]
> [1] 1 2
> Levels: 1 2
> 
> > list(grp.1[mask])
> [[1]]
> [1] 1
> Levels: 1
> 
> It is as though the list were redefining the factor and dropping
> empty levels.  I would like to keep them (I am using the list for a
> two-dimensional tapply). Is there any way to avoid this?
> 
> I'm using R 2.0.0 on FreeBSD 5.2.1.
> 
> Thanks,
> 
> Andrew
> -- 
> Andrew Robinson                      Ph: 208 885 7115
> Department of Forest Resources       Fa: 208 885 6226
> University of Idaho                  E : andrewr at uidaho.edu
> PO Box 441133                        W : http://www.uidaho.edu/~andrewr
> Moscow ID 83843                      Or: http://www.biometrics.uidaho.edu
> No statement above necessarily represents my employer's opinion.
> 
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-- 
Andrew Robinson                      Ph: 208 885 7115
Department of Forest Resources       Fa: 208 885 6226
University of Idaho                  E : andrewr at uidaho.edu
PO Box 441133                        W : http://www.uidaho.edu/~andrewr
Moscow ID 83843                      Or: http://www.biometrics.uidaho.edu
No statement above necessarily represents my employer's opinion.