Hi Michaela,
I understand that you want to fit a linear model to your data that predicts the response variable from the predictor variables, while accounting for the fact that there is a relationship between rows in the data.
The function “stepwiselm” performs stepwise regression and its goal is to find a model that includes only the predictors that significantly contribute to the model, thereby simplifying the model without sacrificing explanatory power. This will not be suitable for your data which has an inherent relationship between rows.
For your dataset, you can use a mixed-effects model, which allows you to include both fixed effects (the predictor variables) and random effects (the subject-specific effects). In MATLAB, you can use the "fitlme" function from the Statistics and Machine Learning Toolbox to fit a linear mixed-effects model.
The relationship information can be fed to the ‘formula’ argument of the "fitlme" function. For more information about the function and relevant examples, please refer to the following documentation page:
Hope it helps!
