This function constructs a diagnostic plot of the adequacy of the Weibull distribution for survival data with respect to one categorical covariate. If the Weibull distribution fits the data well, then the lines produced should be linear and parallel.
A formula containing a
A vector containing labels for the plotted lines.
As discussed in Klein and Moeschberger (2003), one method for checking the adequacy of the Weibull model with a categorical covariate is to produce stratified Kaplan-Meier estimates (KM), which can be transformed to estimate the log cumulative hazard for each stratum. Then in a plot of \log(t) versus \log(-\log(KM)), the lines should be linear and parallel. This can be seen as the log cumulative hazard for the Weibull distribution is
\log H(t) = \log λ + α \log t.
Produces a plot of log Time vs. log Estimated Cumulative Hazard for each level of the predictor
(similarly to what can be obtained using
plot.survfit and the
fun = "cloglog" option),
as well as a data set containing that information.
Sarah R. Haile
Klein, J. and Moeschberger, M. (2003). Survival analysis: techniques for censored and truncated data. Springer.
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