I have what is probably a very simple problem but I would be very grateful to the list for any help or pointers to implement a solution in R.
We have two types of measurements on the eye that we have collected in 62 patients at 5 fixed time points during a clinical visit over an office day. We want to establish if there is an association between the measurements. Obviously it would be wrong to generate a simple scatterplot of all 62*5 observations and consider something like a simple correlation coefficient. What I really need is to set up a 2-level model with measurements nested within patients and use, perhaps, one variable as a response and the other as a predictor. I would also like to add in time of day (probably as a categorical) to check this isn't affecting things. I haven't used multi-level modelling in R and wonder how I can simply go about fitting this model and looking at the significance of the estimates in R. I also have a plot in my mind - 62 little regression lines (n=5) and think that this might be informative..... Any help or pointers will be gratefully received - Many Thanks. Dr. David Crabb Department of Optometry and Visual Science, City University, Northampton Square, London EC1V OHB Tel: 44 207 040 0191 [EMAIL PROTECTED] http://www.city.ac.uk/optometry/about/staff/crabb.html ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
