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The inverse of the cumulative baseline hazard

Source: R/derive-tdt-ttl.R
H0inv_of.Rd

Returns the function that gives the elapsed time at which the cumulative baseline hazard reaches a given value, which is what turns a failure probability into a thermal death time.

Usage

H0inv_of(baseline)

Arguments

baseline

A character string, a key of h0_catalogue: "mem", "weibull", "llogis" or "gompertz".

Value

A function of (x, shape, scale) giving the elapsed time at which the cumulative baseline hazard equals x. shape and scale mean the same as in H0_of():

  • "mem": both are ignored.

  • "weibull" and "llogis": shape is k and scale is s.

  • "gompertz": shape is the rate constant gamma and scale is ignored.

Details

Under the Gompertz baseline with a negative rate constant the cumulative hazard levels off below 1/|gamma|, so a target above that level is never reached. The time returned there is NaN, rather than a large number standing in for "never". A target exactly at the level is reached only after infinite time, and returns Inf.

Examples

# Invert a Weibull baseline (shape 2, scale 60): the time at which H0 reaches 0.25.
H0inv_of("weibull")(x = 0.25, shape = 2, scale = 60)   # 30
#> [1] 30