Hi Emmett,
I understand that you are facing issues while specifying the structure of the matrix of residuals in a Liner Mixed Effects Model.
In MATLAB's "fitlme" function, the "CovariancePattern" argument does indeed relate to the specification of the random effects covariance structure, not the residuals. This is clearly specified in the documentation: https://www.mathworks.com/help/stats/fitlme.html.
When you fit a linear mixed effects model using the "fitlme" function in MATLAB, the estimation procedure automatically estimates the covariance matrix of the residuals based on the specified model and the observed data. MATLAB employs maximum likelihood estimation (MLE) to estimate the model parameters, including the covariance matrix of the residuals.
To obtain the residuals matrix, you can utilize the "residuals" function. This function allows you to extract the residuals from the fitted linear mixed effects model. For further information on the "residuals" function, you can refer to the MATLAB documentation at the following link: https://www.mathworks.com/help/stats/linearmixedmodel.residuals.html.
Hope this helps.
Best Regards,
Yash
