Hazard ratio as a function of time from a parametric survival model

Usage

hr_flexsurvreg(
  x,
  newdata = NULL,
  t = NULL,
  start = 0,
  ci = TRUE,
  B = 1000,
  cl = 0.95,
  na.action = na.pass
)

Arguments

x

Object returned by flexsurvreg or flexsurvspline.

newdata

A data frame with two rows, each specifying a set of covariate values. The hazard ratio is calculated as hazard(z2)/hazard(z1), where z1 is the first row of newdata and z2 is the second row.

newdata must be supplied unless the model x includes just one covariate. With one covariate, a default is constructed, which defines the hazard ratio between the second and first level of the factor (if the covariate is a factor), or between a value of 1 and a value of 0 (if the covariate is numeric).

t

Times to calculate fitted values for. By default, these are the sorted unique observation (including censoring) times in the data - for left-truncated datasets these are the "stop" times.

start

Optional left-truncation time or times. The returned survival, hazard or cumulative hazard will be conditioned on survival up to this time. Predicted times returned with "rmst", "mean", "median" or "quantile" will be times since time zero, not times since the start time.

A vector of the same length as t can be supplied to allow different truncation times for each prediction time, though this doesn't make sense in the usual case where this function is used to calculate a predicted trajectory for a single individual. This is why the default start time was changed for version 0.4 of flexsurv - this was previously a vector of the start times observed in the data.

ci

Set to FALSE to omit confidence intervals.

B

Number of simulations from the normal asymptotic distribution of the estimates used to calculate confidence intervals or standard errors. Decrease for greater speed at the expense of accuracy, or set B=0 to turn off calculation of CIs and SEs.

cl

Width of symmetric confidence intervals, relative to 1.

na.action

Function determining what should be done with missing values in newdata. If na.pass (the default) then summaries of NA are produced for missing covariate values. If na.omit, then missing values are dropped, the behaviour of summary.flexsurvreg before flexsurv version 1.2.

Value

A data frame with estimate and confidence limits for the hazard ratio, and one row for each of the times requested in t.