Hi All,
I am trying to pre-specify / get a better understanding of how to perform a multivariate (3 or 4 outcomes) longitudinal repeated measures analysis where outcomes are measured daily over many months.
If I had just a few time points then my research has guided me towards a random coefficient models in PROC MIXED such as that specified in “Analyzing Multivariate Longitudinal Data Using SAS® “.
But I am struggling to find details of models to account for "continuous" time. I have seen mention of modelling time as a continuous variable, or the use of a splined covariance structure. Would someone mind pointing me in the direction of some appropriate literature in relation to these, or other suggested methodologies please.
Thank you.
time is continuous in the random coefficients model that you mention. You might want to look at brown and prescott's book: https://onlinelibrary.wiley.com/doi/book/10.1002/9781118778210
i'm pretty sure they cover SAS (ie give code examples) and discuss random coefficient models and building a polynomial model for nonlinear relationship with time. Although, im not sure if they discuss the multivariate case
Great thank you so much for your reply and guidance ... I will be looking at the book right away :).
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