[R] Forcing integers to be nominal

[Torsten Hothorn]

> Hi everyone,
> 
> I've got a problem with an analysis of variance where it appears that my
> independent variable is being treated as an integer when it should be
> nominal.
> 

see ?(as.)factor

Torsten

> The data are being loaded from an SPSS file and the independent variable
> 'YearColl' corresponds (surprisingly enough) to a student's year in
> college. :-) The integers 1-4 are used in the dataset for this purpose.
> My quick little anova gives this result:
> 
> > mir.aov <- aov(DepressT ~ YearColl, data=mir)
> > summary(mir.aov)
>              Df  Sum Sq Mean Sq F value   Pr(>F)
> YearColl      1   955.7   955.7  10.305 0.001474 **
> Residuals   293 27172.5    92.7
> ---
> Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1
> 
> I was expecting the df for YearColl to be (k-1) = 3.
> 
> Am I reading this right? Is there a way to force integers to act like
> nominal data?
> 
> -Tim
> 
> -- 
> Tim Wilson      |   Visit Sibley online:   | Check out:
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