[R] Bootstrapping a repeated measures ANOVA

Fischer, Felix Felix.Fischer at charite.de
Fri Apr 16 18:35:34 CEST 2010

Thank you for your answer. Sorry for the missing example.

In fact, i think, i solved the issue by some data-manipulations in the function. I splitted the data (one set for each measuring time), selected the cases at random, and then combined the two measuring times again. Results look promising to me, but if someone is aware of problems, please let me know.

This code should run:

anova.daten=data.frame(subject=sort(rep(1:10,2)), mz=rep(1:2,10), ort=sort(rep(1:2,10)),PHQ_Sum_score=rnorm(20,10,2))  #generate data


 F_values <- function(formula, data1, indices) {
    data2=subset(data1, data1$mz==2)  #subsetting data for each measuring time
    data3=subset(data1, data1$mz==1)
    data4 <- data3[indices,] # allows boot to select sample
    data5=rbind(data3[subjekte,], data2[subjekte,]) #combine data
    data5$subject=factor(rep(1:length(subjekte),2)) #convert repeated subjects to unique subjects
    fit=aov(formula,data=data5)                #fit model
    return(c(summary(fit)[1][[1]][[1]]$`F value`, summary(fit)[2][[1]][[1]]$`F value`))     #return F-values

  results <- boot(data=anova.daten, statistic=F_values,           
     R=10, formula=PHQ_Sum_score~mz*ort+Error(subject/mz))      #bootstrap

Thanks a lot,

Felix Fischer

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