[Rd] Getting ordered factor levels from C

Mark Lilback mlilback at stat.wvu.edu
Wed Oct 24 23:19:44 CEST 2012

I was banging my head for an hour on this. I just pasted the code into an email and see that I was getting the contents of the SEXP for the factor, not the one returned by getAttrib. Sorry for the waste of time.

On Oct 24, 2012, at 4:16 PM, Simon Urbanek <simon.urbanek at r-project.org> wrote:

> 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"  

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

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