When I analyse raz2005
data from mrcorr
package for repeated measures correlation with the following code:
brainvolage.rmc <- rmcorr (participant = Participant, measure1 = Age, measure2 = Volume, dataset = raz2005)
as given in the paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5383908/pdf/fpsyg-08-00456.pdf , I get df=71, which is correct since the number of participants is 72 in this data.
However, when I use the same code for my data, which is structured exactly like raz2005
, I get df=more than 400, although my participant number is 25. I use:
mydata.rmc <- rmcorr (participant = participant, measure1 = measure1, measure2 = measure2, dataset = mydata)
From the paper (page 7), the degrees of freedom should be calculated like this:
N = n_distinct(raz2005$participant)
k = nrow(raz2005)/N
df = N*(k-1)-1
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