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.

f=cfunction(c(foo="factor"), "return getAttrib(foo, R_LevelsSymbol);")
f(lvls)

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"