survival (version 2.41-2)

aeqSurv: Adjudicate near ties in a Surv object

Description

The check for tied survival times can fail due to floating point imprecision, which can make actual ties appear to be distinct values. Routines that depend on correct identification of ties pairs will then give incorrect results, e.g., a Cox model. This function rectifies these.

Usage

aeqSurv(x, tolerance = sqrt(.Machine$double.eps))

Arguments

x

a Surv object

tolerance

the tolerance used to detect values that will be considered equal

Value

a Surv object identical to the original, but with ties restored.

Details

This routine is called by both survfit and coxph to deal with the issue of ties that get incorrectly broken due to floating point imprecision. See the short vignette on tied times for a simple example. Use the timefix argument of survfit or coxph.control to control the option if desired. The rule for `equality' is identical to that used by the all.equal routine. Pairs of values that are within round off error of each other are replaced by the smaller value. An error message is generated if this process causes a 0 length time interval to be created.

See Also

survfit, coxph.control