How to calculate regression slopes by subject in table with many subjects each measured at different ages?
Renal function is measured as Glomerular Filtration rate (GFR) and loss of function in renal disease is estimated as the (negative) slope of GFR by advancing age. In studies of kidney disease, it is often the objective to test for baseline predictors of the slope of GFR by age or time. The attached table shows typical data for 10 subjects with each having GFR measured at two or more ages. Can anyo...