R/surv.ss.r

In alasorous/samplesize: Sample size calculations for continuous, binary, count and survival data

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##  Functions for survival data sample size calculations
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##  Author: Alex Godwood
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##  Date: 16 Dec 2010
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##  Survival sample size

surv.ss <- function(alpha, power, HR, r){
  theCall <- match.call()
  print(theCall)
  events.req <- (((r+1)*(qnorm(1-alpha/2)+qnorm(power)))/(sqrt(r)*log(HR)))^2
  chr <- exp(-1*((r+1)*(qnorm(1-alpha/2)))/sqrt(r*events.req))
  res <- data.frame(alpha, power, HR, r, events=events.req, criticalHR= chr)
  return(res)
}
#surv.ss(alpha=0.05, power=0.9, HR=0.8, r=1)