[R] How to take the lower triangular part from a full matrix

Dear all: I have a question regarding on how to take the lower triangular part from a full matrix. for example 1 2 3 1 0 0 3 4 5 to 3 4 0 7 8 9 7 8 9 Thanks, Joey [[alternative HTML version deleted]] _

[R] Modifyiing R working matrix within "gee" source code

Dear all, I am working on modifying the R working matrix to commodate some other correlations that not included in the package. I am having problem to locate where the R matrix are defined for regular matrices, i.e. independence, exchangeable, AR and unstructure. it might have something within .C(

[R] How to generate longitudinal data using R

How to generate the longitudinal data with correlation structure of independent , exchangeable and AR (1) through errors? Can someone provide some sample codes? Great appreciation! Thanks much, Yi [[alternative HTML version deleted]] __ R-help@

[R] How to get the standard error from GEE(Generalized Estimation Equations) output

I am having some difficulties to locate the standard error from GEE output. ---sample output using list (geemodel) Link: Identity Variance to Mean Relation: Gaussian Correlation Structure: Exchangeable Call: gee(formula = days.sick1 ~ bm