[R] glm for nominal X ordinal

[Gang Chen]

Thanks a lot! This is exactly what I wanted.

Gang


On Jan 5, 2008, at 2:20 PM, David Winsemius wrote:

> Gang Chen <gangchen at mail.nih.gov> wrote in
> news:4B1D9D53-7F9A-4337-912A-B7D29601DC25 at mail.nih.gov:
>
>> Suppose I have a two-way table of nominal category (party
>> affiliation) X ordinal category (political ideology):
>>
>> party affiliation X (3 levels) - democratic, independent, and
>> republic
>> political ideology Y (3 levels) - liberal, moderate, and
>> conservative
>>
>> The dependent variable is the frequency (or count) for all the two-
>> way cells sampled from the voters. I want to test whether there is
>> any party affiliation effect, and, if there is, the pair-wise
>> contrasts. I have never used glm (I assume this the program I should
>>  use) before, so I am not so sure how I can code the two independent
>>  variables reflecting the fact that one is nominal while the other
>> is  ordinal and how to formulate the model.
>
> ?factor
>
> Set up affiliation as a factor and ideology as an ordered factor. The
> levels argument in factor sets the sort order.
>
>> theo<-c("cons", "mod", "cons", "cons", "lib", "mod")
>> table(theo)
> theo
> cons  lib  mod
>    3    1    2
>
>> theo<-ordered(theo, levels=c("lib", "mod", "cons"))
>> table(theo)
> theo
>  lib  mod cons
>    1    2    3
>
>  The formula  in glm would be something similar to counts ~ theo +  
> affil
>
> Much more detail and worked examples regarding modeling count data  
> would
> be found in:
> Thompson, LA;  (2004) R (and S-PLUS)Manual to Accompany Agresti’s  
> (2002)
> Catagorical Data Analysis;
> https://home.comcast.net/~lthompson221/Splusdiscrete2.pdf
>
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