Survreg/psm output
Laura Bonnett wrote:
Dear R-listers, I know that there have been many, many posts on the output from Survreg. To summarise what I have read, Scale is 1/shape of the Weibull which is also the standard deviation of the normal distribution which is also the standard deviation of the log survival time and Intercept is log(scale). I also know that the hazard function can be calculated from the output to give something like: h(time)=exp(-intercept)^scale x scale x time^(1-scale) So, for example if the intercept was -1.11 and the scale was 1.17 then the hazard function is h(t) = exp(1.11)^1.17 x 1.17 x t^0.17 = 4.30 t^0.17 However, how can I work out what the hazard is I.e. by how much does the risk of death increase or decrease with time? Some people have said that is the scale parameter is greater than 1 then the risk of death increases with age. Is this correct? I am also aware that Harrell has posted previously that there is a case study in his book. I have a copy of the book and have read all the case studies but I'm still not convinced I know what the hazard of death is?!
library(Design) f <- psm(...) h <- Hazard(f) # fitted hazard function as an R function h # look at it Evaluate h at any time and any linear predictor (the latter being computed by for example predict(f, newdata)). Frank
Sorry that this relates to previously posted queries, but as yet there doesn't seem to be a satisfactory solution to the question of the output? Thank you for your help as always, Laura
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University