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Dear r-help subscribers, A couple of weeks ago I sent the following message to the r-help mail list. It hasn't generated any response, and I could really use some help on this. Anyone able to help? Thanks again, Roger Dungan >> I am working on some survival analysis of some interval censored failure time data in R. I have done similar analysis before using PROC LIFEREG in SAS. In that instance, a gamma survival function was the optimum parametric model for describing the survival and hazard functions. I would li...

...<-subset(x, is.na(x)==F) >sd(y) [1] 1.707825 Am I missing something, or is this a problem with sd()? Why does mean(x) give a simple NA, but var(x) requires some additional work? There was some previous discussion in r-help about this for R v 1.6.0, with mention of a fix for 1.6.1. Dr Roger Dungan School of Biological Sciences University of Cantebury Christchurch, New Zealand ph +64 3 366 7001 ext. 4848 fax +64 3 364 2590

...;) At least one of the R-help listserver comments mentioned using survreg.distributions to customise a gamma distribution, but I can't figure out how to make this work with the resources (intellectual and bibliographical!) that I have available. With thanks in advance for your help, Dr Roger Dungan School of Biological Sciences University of Cantebury Christchurch, New Zealand ph +64 3 366 7001 ext. 4848 fax +64 3 354 2590