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    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...
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    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...
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    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 <-...
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    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...
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    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...
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    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...
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    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...