In your book, section 8.8 (Cholesky Transformation) did use the following to generate uncorrelated random intercepts and slopes. U = RandNormal(m, {0 0}, Sigma);  /* random intercepts and slopes */   But, the last paragraph on page 18 of the attached article has parameter r1, r2, r3 for random intercepts, slopes, and fitted longitudinal value at the event time W1i(t) respectively.   How can you connect the above 2x2 matrix of U with W1i(t)?     ... View more