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1. summing two probability density functions---Gompertz hazard model?

Hi, r-help members. I have a question about summing two density distributions. I have two samples from which I've estimated hazard parameters for a Gompertz mortality model. With those parameters, I can calculate the PDF (survival function times hazard function) of ages-at-death in a birth...
2. looping a procedure that utilizes an integration of a function

Hi, all. I've written a function that returns the survival function for a Gompertz mortality model. I've specified the two model parameters. With a calculation that includes a simple integration, I can calculate the life expectancy at any age. Is there a way I can use a loop with the...
3. log-rank (or other) test for difference between survival curves

Hi, all. I have co-opted some R code that estimates parameters for a Gompertz-Makeham mortality model. The data to which the model is fit is interval censored, with counts of individuals in each age-range category. For example: naga <-...
4. multivariate ordered probit regression---use standard bivariate normal distribution?

Hello. My two previous posts (1 & 2) have about 100 views each, but no replies, so I must have done a poor job asking the question. So, here is the general question: how can I run a run a multivariate (more than one non-independent, response variables) ordered probit regression model? I've...
5. unrestricted cumulative probit model with vglm()---extend to a multivariate setting?

Hello. I'm trying to fit a multivariate, unrestricted cumulative probit model. I've had success in fitting a proportional odds probit model using polr(method="probit") in the MASS package and the unrestricted cumulative probit model using vglm(cumulative(link="probit)) in the VGAM package...
6. unrestricted cumulative probit model with vglm()---extend to a multivariate setting?

Hi, all. I'm trying to model the transition of multiple, ordinal response variables on a continuous predictor (age). In this specific case, I'm investigating the ages at which a skeletal trait passes through a series of morphological stages. In anthropological parlance, this has become known...
7. multivariate ordinal probit regression with vglm()

Hello, all. I'm investigating the rate at which skeletal joint surfaces pass through a series of ordered stages (changes in morphology). Current statistical methods in this type of research use various logit or probit regression techniques (e.g., proportional odds logit/probit...