Error when running a repeated measures ANOVA

Hello, I need to run a repeated measure ANOVA with three independent factors, but I'm struggling to make my code work even with just one factor.

Below is my code.

words is a matrix with columns corresponding to patient IDs (integers 1-205). Vowel, Treatment, and Test are all factors, but are replaced with a number (ex. Test can take the value 1, 2, or 3). Test is the repeated measure "time" variable. MD is the dependent outcome variable.

I tried running my ANOVA without including other factors at first, following along with other examples, I've seen. I keep getting the error:

"Error using RepeatedMeasuresModel/set.WithinDesign (line 1235) Specified design has 3 points; 1 required. "

I guess I don't understand the role of WithinDesign very well. Could someone help me out a bit?

Thank you!

words = array2table(words);
stories = array2table(stories);

words.Properties.VariableNames(1:5) = {'ID','Vowel','Treatment','Test','MD'};

withinDsgn = table((1:3)','VariableNames',{'Test'});

wordsrm = fitrm(words, 'MD~ID*Test', 'WithinDesign', withinDsgn);

Answer 1

[Jeff Miller]

I'm pretty sure fitrm expects all of the data from a single patient to be on one row of the input data table (e.g., words)--at least by default, maybe there is some way around this. So, for your example with 3 tests, it would expect 3 separate columns of data, say Test1, Test2, Test3, and a command like

wordsrm = fitrm(words,'Test1-Test3 ~ ID','WithinDesign', withinDsgn)

Your fitrm command only specified one score (MD), so fitrm thought the WithinDesign 'required' only one condition per patient, and it was confused because your WithinDesign specifies 3 conditions.

Additional repeated measures factors would multiply the number of columns to the left of the '~' in the model statement.

[pablo dopico]

Thank you!

So for additional factors I would need a column for every factor-time? Ex. Vowel1*Treatment1*Test1 as one column, then Vowel1*Treatment1*test2, etc?

So with multiple factors this would be:

wordsrm = fitrm(words, 'Column1-ColumnN ~ ID', 'WithinDesign',withinDsgn)

wordsanova = ranova(wordsrm, 'WithingDesign', withinDsgn)

[Jeff Miller]

Right. And you need to specify that the variables of WithinDesign are categorical. The example here may help.

[pablo dopico]

Thanks so much for your help, I'll give this a shot, i think I understand this much better now.