To create an exponential survival object the following
options are available:
scale and shape to specify the canonical parameters of the distribution, or
surv, t and shape for the proportion surviving (no events) at time t and the shape parameter, or
fail, t and shape for the proportion failing (events) at time t and the shape parameter or
intercept and scale for the parameters returned by survreg(.., dist = "weibull") models.
scale = -log(surv)/(t^shape)
scale = -log(1-fail)/(t^shape)
The parameters should be spell correctly as partial matching is not available