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Estimate plausible piecewise constant hazard rates from summary summary event proportions

Source: R/prop_to_haz.R
prop_to_haz.Rd

Given estimates of the event probability at one or more fixed times, the corresponding piecewise hazard rates can be determined through closed-form formulae. This utility function can be useful when simulating trial datasets with plausible event rates.

Usage

prop_to_haz(probs, cutpoints = 0, endtime)

Arguments

probs

vector. Probabilities of the event (i.e. cumulative incidence probabilities) at one or more time point. If only a single value is given, then it is assumed that this is the probability at the endtime.

cutpoints

vector. Times at which the baseline hazard changes. Default is cutpoints = 0, which corresponds to a simple (non-piecewise) exponential model.

endtime

scalar. Time at which final element in probs corresponds to. Typically this would be the study endpoint time.

Value

Vector of constant hazard rates for each time piece defined by cutpoints.

Details

Given \(J-1\) internal cut-points, then there are J intervals defined as: \([s_0, s_1)\), \([s_1, s_2)\), \(\dots\), \([s_{J-1}, s_{J})\), with conditions that \(s_0 = 0\) and \(s_J = \infty\). Each interval corresponds to constant hazard \(\lambda_j\).

Examples

lambda <- prop_to_haz(0.15, endtime = 36) # 15% probability at 36-months
all.equal(pexp(36, lambda), 0.15)
#> [1] TRUE

# 15% probability at 12-months, and 30% at 24-months
prop_to_haz(c(0.15, 0.30), c(0, 12), 24)
#> [1] 0.01354324 0.01617967
PWEALL::pwe(12, prop_to_haz(c(0.15, 0.30), c(0, 12), 24), c(0, 12))$dist
#> [1] 0.15
PWEALL::pwe(24, prop_to_haz(c(0.15, 0.30), c(0, 12), 24), c(0, 12))$dist
#> [1] 0.3