[R] ANCOVA with defined error terms

hpdutra hpdutra at yahoo.com
Thu Aug 20 04:46:42 CEST 2009


I am trying to run an ANCOVA with defined error terms.  Thus I have to use
AOV and not lm. 
my response variable is proportion of mice paw prints on track plates. These
plates were placed on plots that had vegetation and fruit manipulated to two
levels each (present or absent), and were sampled monthly for 14 months
(repeated measures). The fully crossed factor design was also blocked. My
sample size is just 3 and I cannot run the full model because I would ran
out of degrees of freedom. 
I measured raccoon activity on these plots as a covariate. So I am running
the following model.


summary(model<-(aov(mice~veget*fruit*time+(time*block)+(time*block*veget)+(time*block*fruit)+coon+Error(block/plot,
data = track))))

here is a sample of the data 
plot	veget	        fruit	     time	block 	coon     	        mice 
p1	Vremoved	Fintact	1	b1      	8.605276544	26.67179738
p2	Vintact	Fintact	1	b1 	     	16.64929378	45
p3	Vremoved	Fremoved	1	b1 	     	22.12023855	26.67179738
p4	Vintact	Fremoved	1	b1 	     	16.64929378	41.57117579
p5	Vintact	Fremoved	1	b2 	     	30.73522506	38.09196076
p6	Vremoved	Fintact	1	b2 	     	22.12023855	26.67179738
p7	Vintact	Fintact	1	b2 	     	8.605276544	8.605276544
p8	Vremoved	Fremoved	1	b2 	     	8.605276544	8.605276544
p9	Vintact	Fintact	1	b3 	     	8.605276544	16.64929378
p10	Vintact	Fremoved	1	b3 	        16.64929378	8.605276544
p11	Vremoved	Fintact	1	b3     	8.605276544	30.73522506
p12	Vremoved	Fremoved	1	b3  	     	8.605276544	16.64929378
p1	Vremoved	Fintact	2	b1       	22.12023855	41.57117579
p2	Vintact	Fintact	2	b1  	     	8.605276544	48.42882421

My question is. Is there a more simple way to run this mess using lm or not?



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