[R] re form data for aov()?

[Dan Kelley]

As a followup, I show below what I get if I "break out" the variables by
making a new data frame with new (boolean) columns that indicate the
treatment.  (The experiment was germ count on hands, after cleansing with 4
different methods.)

What I'm hoping is to find a way to do this in a less "hard-wired" way (i.e.
in which I do not have to change my code for every application, explicitly
naming the factors).


> dd<-data.frame(d, Alcohol.Spray=d$Method=="Alcohol.Spray",
> Antibacterial.Soap=d$Method=="Antibacterial.Soap",
> Soap=d$Method=="Soap",Water=d$Method=="Water")
> 
> anova(aov(Bacterial.Counts ~ Alcohol.Spray+Antibacterial.Soap+Soap+Water,
> data=dd))
Analysis of Variance Table

Response: Bacterial.Counts
                   Df Sum Sq Mean Sq F value    Pr(>F)    
Alcohol.Spray       1  27473   27473 19.4822 0.0001374 ***
Antibacterial.Soap  1   1925    1925  1.3653 0.2524658    
Soap                1    484     484  0.3432 0.5626651    
Residuals          28  39484    1410                      
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 
> 


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