Richard Pitman <richard.pitman3 <at> btopenworld.com> writes: > > I am new to R and am trying to fit a survival curve with a weibull > hazard function to a set of data giving the probability of survival to > age x, given the year of birth, in the form: > > Probability of survival: > Birth year > 1980 1981 ... 2003 > .2 0.90 0.89 ... 0.87 > 1 0.80 0.81 ... 0.79 > age 2 0.75 0.74 ... 0.73 > 3 0.70 0.69 ... 0.68 > 5 0.50 0.49 ... 0.43 > 10 0.30 0.31 ... 0.26 > > I would like to be able to fit a curve to each birth cohort, extrapolate > the curve a few years and be able to create a plot of the survival > curves. >
You don't have enough data for a standard survival analysis, which is based on individual-level survival times. (You don't even know the total cohort size, which you would need to know to fit a binomial model.) However, you can compute the _expected_ probabilities of survival to age a using dweibull(a) [or, since your categories are fairly coarse, pweibull(a2)-pweibull(a1)]. As a starting point, you could try a least-squares fit through the data -- again, this is not quite right, but in the absence of information about sample size it's a little hard to know how to weight the different points. Hope that helps. Ben Bolker ______________________________________________ [email protected] 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.
