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Hi there, Does anyone know if there is a package in R for multi-demensional Gaussian quadrature? I checked out the package "gaussquad" but it can only do 1D. Thanks! Lei Liu Associate Professor Division of Biostatistics Department of Public...

Hi there, I have a dataset from a longitudinal study with a lot of drop-out. I want to implement the inverse probability weighting method by Robins 1995 JASA paper "Analysis of semiparametric regression models for repeated outcomes in the...

Hi, I am using coxph in simulations and I want to store the "robust se" (or "se2" in frailty models) for each replicate. Is there a function to retrieve it, like vcov() for the variance estimate? Thanks! Lei Liu Assistant...

Hi there, I have a question on manipulating a matrix. Say I have a matrix A with 3 rows. I want to generate a new matrix B with 3 duplicates of the first row of A, 2 duplicates of the...

Hi there, I want to install the "adapt" package, which is available at http://cran.r-project.org/src/contrib/Archive/adapt/. This package cannot be directly installed by "install packages" menu in R. So I downloaded the zip file...

Hi there, I have a question on the frailty model for gap times with distinct baseline hazard for each gap. Can I use R coxph function to do it? For example, the following code assumes an identical baseline hazard for...

Hi there, After I fitted a cox model, I used vcov to obtain the variance of the parameter estimate. It worked correctly in R 1.9.1. But it failed in R 2.0.0 and the error message is...

Hi there, I want to make trajectory plots for data as follows: ID time y 1 1 1.4 1 2 2.0 1 3 2.5 2 1.5 2.3 2 4 4.5 2 5.5 1...

Hi there, I have a question on cross over design. There are 3 treatments, each with 3 dose levels, a total of 27 treatment combinations. Each treatment combination is given to a subject in 1 day. However, we can only...

Hi there, Thank you all for your timely response. I find the right way to do it. There is a good example in Dr. Burns website: http://www.burns-stat.com/pages/Spoetry/Spoetry.pdf Page 174. So this is...

Hi there, I have a question on fitting data by coxme. In particular I want to fit a random intercept and random slope cox model. Using the rats dataset as an example, I generated another covariate x2 and want to...

Hello, I need to call an C function MH.c in my R code in Windows XP. I downloaded the software form http://www.stats.ox.ac.uk/pub/Rtools/ and installed them. But when I run the command "..\bin...

Hi there, I am using SAS Proc NLMIXED to maximize a likelihood with multivariate normal random effects. An example is the two part random effects model for repeated measures semi-continous data with a cluster at 0. I use the...

Hi there, I have two questions on matrix manipulation. For the first one, I want to calculate the product of each column of a matrix (say A) with another vector (say b). That is, if A has 5 columns (a1...

Hi there, I want to call a C function in R. I have some experience on it, but this time I need to call another C function in the "main" C function. As a simple example, I use the following...

Hi there, I am reading the 2004 paper "Smoothing with mixed model software" in Journal of Statistical Software, by Ngo and Wand. I tried to run their first example in Section 2.1 using R but I had some problems...

Hi there, I tried to fit a penalized spline for a continuous risk factor in recurrent events data. I found that I can include both pspline and frailty terms in coxph. So I use code like fit1 <- coxph(Surv(start...

Hi there, I have a question on how to extract the linear term in the penalized spline in coxph. Here is a sample code: n=100 set.seed(1) x=runif(100) f1 = cos(2*pi*x) hazard = exp(f1...