[R] Repeated Measures ANOVA and Missing Values in the data set

[Stéphane Adamowicz]

This happens because your model should be :

aov.out = aov(values ~ time + Error(subject), data=mydata2)

This will not generate any error.
However, you should be aware that aov is not suitable for unbalanced data, for which it will give inconsistent results.

In such case, you can use the lme function :

require(nlme)
aov2 <- lme(fixed= values~time, random=~1|subject, na.action=na.omit, data=mydata2)
summary(aov2)
anova(aov2)


Le 19 juin 2015 à 02:42, gianni lavaredo <gianni.lavaredo at gmail.com> a écrit :

> I am doing Repeated Measures ANOVA with missing values. When i run my model
> i get this error message.
> 
> 
> 
> 
> *aov.out = aov(values ~ time + Error(subject/time), data=mydata2)Warning
> message:In aov(values ~ time + Error(subject/time), data = mydata2) :
> Error() model is singular*
> 
> The missing Values are not a error of my instrument. They mean the element
> of my analysis is absent and i want to consider this.
> 
> thanks in advance
> 
> these are my data:
> 
> subject <- c(1,2,3,4,5,6,7,8,9,10)
> time1 <- c(5040,3637,6384,5309,5420,3549,NA,5140,3890,3910)
> time2 <- c(5067, 3668, NA, 6489, NA, 3922, 3408, 6613, 4063, 3937)
> time3 <- c( 3278, 3814, 8745, 4760, 4911, 5716, 5547, 5844, 4914, 4390)
> time4 <- c(   0, 2971,    0, 2776, 2128, 1208, 2935, 2739, 3054, 3363)
> time5 <- c(4161, 3483, 6728, 5008, 5562, 4380, 4006, 7536, 3805, 3923)
> time6 <- c( 3604, 3411, 2523, 3264, 3578, 2941, 2939,   NA, 3612, 3604)
> mydata <- data.frame(time1, time2, time3, time4, time5, time6)
> mydata2 = stack(mydata)
> subject  = factor(rep(subject,6))
> mydata2[3] = subject
> colnames(mydata2) = c("values", "time", "subject")
> aov.out = aov(values ~ time + Error(subject/time), data=mydata2)
> summary(aov.out)
> model.tables(aov.out,"means")
> 
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> 
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Stéphane Adamowicz
Chercheur / Scientist
stephane.adamowicz at paca.inra.fr
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