I have a data set of 100 subjects and each subject has 27 observations. But the observation time (I use the "age" when they got the exam here ) are different for each subject.The minimum age is 29 and maximum age is 96 in the data.
data are like this: SubjID obs1-obs27 age1-age7
My question is:
How to specify the basis? Here each subject has different observation time although they have same number of observations.
Before I use it, I specify the b-spline basis:
Then I run smooth.basisPar
But I got the error message;
Error in bsplineS(evalarg, breaks, norder, nderiv, returnMatrix) : Knots do not span the values of X