R devel - Oct 2012 - Getting ordered factor levels from C

I'm working on an R package in C and can't seem to get the same level
information about a factor that the R console displays.

If I define a factor as:

lvls <-
factor(c('red','blue','blue','green','red'),
c('blue','green','red'), ordered=TRUE)

When I get the "levels" attribute in C, I get back the the first
vector, not the second. If I run attr(lvls,"levels") in R, I get back
the second vector. There are no attributes besides class and levels, so how do I
get the list of levels in the correct order?

Thanks

-- 
Mark Lilback
West Virginia University Department of Statistics
mlilback at stat.wvu.edu

On Oct 24, 2012, at 2:14 PM, Mark Lilback wrote:
> I'm working on an R package in C and can't seem to get the same
level information about a factor that the R console displays.
> 
> If I define a factor as:
> 
> lvls <-
factor(c('red','blue','blue','green','red'),
c('blue','green','red'), ordered=TRUE)
> 
> When I get the "levels" attribute in C, I get back the the first
vector, not the second.
What are you using in C? AFAICS it works just fine:
> f=cfunction(c(foo="factor"), "return getAttrib(foo,
R_LevelsSymbol);")
> f(lvls)
[1] "blue"  "green" "red"  

Cheers,
Simon


> If I run attr(lvls,"levels") in R, I get back the second vector.
There are no attributes besides class and levels, so how do I get the list of
levels in the correct order?
> 
> Thanks
> 
> -- 
> Mark Lilback
> West Virginia University Department of Statistics
> mlilback at stat.wvu.edu
> 
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