[R] Dúvida função Anova pacote car - Medidas repetidas

[John Fox]

Dear Diego,

This is close enough to Spanish for me to understand it (I think).

Using Anova() in the car package for repeated-measures designs requires a
multivariate linear model for all of the responses, which in turn requires
that the data set be in "wide" format, with each response as a variable. In
your case, there are two crossed within-subjects factors and no
between-subjects factors. If this understanding is correct (but see below),
then you could proceed as follows, where the crucial step is reshaping the
data from "long" to "wide":

------------- snip --------------

Pa2$type.day <- with(Pa2, paste(Type, Day, sep="."))
(Wide <- reshape(Pa2, direction="wide", v.names="logbiovolume",
idvar="Replicate", timevar="type.day", drop=c("Type", "Day")))

day <- ordered(rep(c(0, 2, 4), each=2))
type <- factor(rep(c("c", "t"), 3))
(idata <- data.frame(day, type))

mod <- lm(cbind(logbiovolume.c.0, logbiovolume.t.0, logbiovolume.c.2,
logbiovolume.t.2, logbiovolume.c.4, logbiovolume.t.4) ~ 1, data=Wide)

Anova(mod, idata=idata, idesign=~day*type)

------------- snip --------------

This serves to analyze the data that you showed; you'll have to adapt it for
the full data set.

I'm assuming that the "replicates" are independent units, and that the
design is therefore entirely within replicate. If that's wrong, then the
analysis I've suggested is also incorrect.

I hope this helps,
 John

-----------------------------------------------
John Fox
Senator McMaster Professor of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada




> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Diego Pujoni
> Sent: Friday, October 05, 2012 9:57 AM
> To: r-help at r-project.org
> Subject: [R] Dúvida função Anova pacote car - Medidas repetidas
> 
> Ola pessoal, estou realizando uma ANOVA com medidas repetidas e estou
> utilizando a fungco "Anova" do pacote "car".
> 
> Medi o biovolume de algas a cada dois dias durante 10 dias (no banco de
> dados abaixo ss coloquei ati o 40 dia). Tenho 2 tratamentos ("c","t") e
> o
> experimento foi realizado em triplicas ("A","B","C").
> 
> > Pa2
>    Day Type Replicate logbiovolume
> 1    0    c         A        19.34
> 2    0    c         B        18.27
> 3    0    c         C        18.56
> 4    0    t         A        18.41
> 5    0    t         B        18.68
> 6    0    t         C        18.86
> 7    2    c         A        18.81
> 8    2    c         B        18.84
> 9    2    c         C        18.52
> 10   2    t         A        18.29
> 11   2    t         B        17.91
> 12   2    t         C        17.67
> 13   4    c         A        19.16
> 14   4    c         B        18.85
> 15   4    c         C        19.36
> 16   4    t         A        19.05
> 17   4    t         B        19.09
> 18   4    t         C        18.26
> .
> .
> .
> 
> Pa2.teste = within(Pa2,{group = factor(Type)
>                    time = factor(Day)
>                    id = factor(Replicate)})
> matrix =
> with(Pa2.teste,cbind(Pa2[,VAR][group=="c"],Pa2[,VAR][group=="t"]))
> matrix
>        [,1]  [,2]
>  [1,] 19.34 18.41
>  [2,] 18.27 18.68
>  [3,] 18.56 18.86
>  [4,] 18.81 18.29
>  [5,] 18.84 17.91
>  [6,] 18.52 17.67
>  [7,] 19.16 19.05
>  [8,] 18.85 19.09
>  [9,] 19.36 18.26
> [10,] 19.63 18.96
> [11,] 19.94 18.06
> [12,] 19.54 18.37
> [13,] 19.98 17.96
> [14,] 20.99 17.93
> [15,] 20.45 17.74
> [16,] 21.12 17.60
> [17,] 21.66 17.33
> [18,] 21.51 18.12
>  model <- lm(matrix ~ 1)
>  design <- factor(c("c","t"))
> 
>  options(contrasts=c("contr.sum", "contr.poly"))
>  aov <- Anova(model, idata=data.frame(design), idesign=~design,
> type="III")
>  summary(aov, multivariate=F)
> 
> Univariate Type III Repeated-Measures ANOVA Assuming Sphericity
> 
>                  SS num Df Error SS den Df         F    Pr(>F)
> (Intercept) 12951.2      1   6.3312     17 34775.336 < 2.2e-16 ***
> design         19.1      1  17.3901     17    18.697 0.0004606 ***
> ---
> Signif. codes:  0 *** 0.001 ** 0.01 * 0.05 . 0.1   1
> 
> 
> O problema i que eu acho que esta fungco nco esta levando em
> consideragco
> os dias, nem as riplicas. Como fago para introduzir isto na analise.
> Vocjs
> conhecem alguma fungco correspondente nco paramitrica para este teste?
> Tipo
> um teste de Friedman com dois grupos (tratamento e riplica) e um bloco
> (tempo)?
> 
> Muito Obrigado
> 
>                                                Diego PJ
> 
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