[R] Extracting F and p from aov() - tricksy solution

[Peter Dalgaard BSA]

Mark Myatt <mark at myatt.demon.co.uk> writes:

> Liqing Zhang <lzhang at ea.oac.uci.edu> writes:
> >
> >I performed an aov() analysis and got the following results:
> >
> >            Df Sum Sq Mean Sq F value Pr(>F)
> >block         1 0.0040  0.0040  0.3282 0.5672
> >Residuals   269 3.2766  0.0122
> >
> >Can anyone tell me how to extract the F value column and Pr(>F) column
> >from the summary output of aov analysis?
> 
> I thought that would be easy but the summary() object of aov() seems to
> be an odd beast. Fiddling around I came up with this:
> 
> data(warpbreaks)
> LZ.aov <- summary(aov(breaks ~ wool + tension, data = warpbreaks))
> LZ.aov.fp <- cbind(LZ.aov[[1]]$"F value", LZ.aov[[1]]$"Pr(>F)")
> colnames(LZ.aov.fp) <- c("F", "p")
> 
> All we need now is to get the right row-names. I suppose that will
> require a function that will extract the variable names from the
> formula.

Ummm,

> as.matrix(LZ.aov[[1]][4:5])
             F value      Pr(>F)
wool        3.339316 0.073613669
tension     7.536651 0.001377778
Residuals         NA          NA

(or as.data.frame(), or just use LZ.aov[[1]][4:5] and ignore the
significance stars...)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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