sdlog: Standard deviation on the log scale (log normal)
scale: Scale parameter (Weibull)
Returns
Hazard (functions beginning 'h') or cumulative hazard (functions beginning 'H').
Details
For the exponential and the Weibull these are available analytically, and so are programmed here in numerically stable and efficient forms.
For the gamma and log-normal, these are simply computed as minus the log of the survivor function (cumulative hazard) or the ratio of the density and survivor function (hazard), so are not expected to be robust to extreme values or quick to compute.