ezANOVA runs but converts subj into factor

[Han]

Hi, 

I've just started using R a few days ago and am trying to run a one-way repeated measures ANOVA.

Tried using ezANOVA but I'm stuck on a problem.

From my understanding, the data needs to be arranged in the long form (correct?), like this:

I did that. Then I tried running the one-way repeated measures ANOVA like this:

w_anova<-ezANOVA(data=df, dv=breakN, wid=subnum, within=Mask, type=3, detailed=T, return_aov = T)

print(w_anova)

It gives a warning:" Converting "subnum" to factor for ANOVA." 

The results for the within-subjects factor is comparable to MATLAB, but the conversion changes the Sums of Squares for Subjects.

Not entirely sure how to interpret this and troubleshoot. Please advise.

Many thanks!

 

[Mike Lawrence]

What you've done seems right to me. Since the subject labels are only numbers for convenience (i.e. subject #10 isn't 2x subject #5, etc), when ez encounters numbers in a column to be used as the "wid" variable it gives you a heads up that it's going to do the conversion for you. If Matlab is giving you different sums of squares, I wonder if it's treating the labels as true numbers, which would yield an incorrect analysis.

--
Mike Lawrence
Graduate Student
Department of Psychology & Neuroscience
Dalhousie University

~ Certainty is (possibly) folly ~

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