### confint.predictCox.R ---
##----------------------------------------------------------------------
## Author: Brice Ozenne
## Created: maj 23 2018 (14:08)
## Version:
## Last-Updated: Jan 29 2019 (10:49)
## By: Thomas Alexander Gerds
## Update #: 262
##----------------------------------------------------------------------
##
### Commentary:
##
### Change Log:
##----------------------------------------------------------------------
##
### Code:
## * confint.predictCox (documentation)
##' @title Confidence Intervals and Confidence Bands for the predicted Survival/Cumulative Hazard
##' @description Confidence intervals and confidence Bands for the predicted survival/cumulative Hazard.
##' @name confint.predictCox
##'
##' @param object A \code{predictCox} object, i.e. output of the \code{predictCox} function.
##' @param level [numeric, 0-1] Level of confidence.
##' @param parm [character] the type of predicted value for which the confidence intervals should be output.
##' Can be \code{"survival"} or \code{"cumhazard"}.
##' @param cumhazard.transform [character] the transformation used to improve coverage
##' of the confidence intervals for the cumlative hazard in small samples.
##' Can be \code{"none"}, \code{"log"}.
##' @param survival.transform [character] the transformation used to improve coverage
##' of the confidence intervals for the survival in small samples.
##' Can be \code{"none"}, \code{"log"}, \code{"loglog"}, \code{"cloglog"}.
##' @param nsim.band [integer, >0] the number of simulations used to compute the quantiles for the confidence bands.
##' @param seed [integer, >0] seed number set before performing simulations for the confidence bands.
##' If not given or NA no seed is set.
##' @param ... not used.
##'
##' @details The confidence bands and confidence intervals are automatically restricted to the interval of definition of the statistic,
##' i.e. a confidence interval for the survival of [0.5;1.2] will become [0.5;1].
##'
##'
##' @author Brice Ozenne
## * confint.predictCox (examples)
##' @rdname confint.predictCox
##' @examples
##' library(survival)
##'
##' #### generate data ####
##' set.seed(10)
##' d <- sampleData(40,outcome="survival")
##'
##' #### estimate a stratified Cox model ####
##' fit <- coxph(Surv(time,event)~X1 + strata(X2) + X6,
##' data=d, ties="breslow", x = TRUE, y = TRUE)
##'
##' #### compute individual specific survival probabilities
##' fit.pred <- predictCox(fit, newdata=d[1:3], times=c(3,8), type = "survival",
##' se = TRUE, iid = TRUE, band = TRUE)
##' fit.pred
##'
##' ## check standard error
##' sqrt(rowSums(fit.pred$survival.iid[1,,]^2)) ## se for individual 1
##'
##' ## check confidence interval
##' newse <- fit.pred$survival.se/(-fit.pred$survival*log(fit.pred$survival))
##' cbind(lower = as.double(exp(-exp(log(-log(fit.pred$survival)) + 1.96 * newse))),
##' upper = as.double(exp(-exp(log(-log(fit.pred$survival)) - 1.96 * newse)))
##' )
##'
##' #### compute confidence intervals without transformation
##' confint(fit.pred, survival.transform = "none")
##' cbind(lower = as.double(fit.pred$survival - 1.96 * fit.pred$survival.se),
##' upper = as.double(fit.pred$survival + 1.96 * fit.pred$survival.se)
##' )
##'
## * confint.predictCox (code)
##' @rdname confint.predictCox
##' @method confint predictCox
##' @export
confint.predictCox <- function(object,
parm = NULL,
level = 0.95,
nsim.band = 1e4,
cumhazard.transform = "log",
survival.transform = "loglog",
seed = NA,
...){
if(object$se[[1]] == FALSE && object$band[[1]] == FALSE){
message("No confidence interval/band computed \n",
"Set argument \'se\' or argument \'band\' to TRUE when calling predictCox \n")
return(object)
}
## ** check arguments
dots <- list(...)
if(length(dots)>0){
txt <- names(dots)
txt.s <- if(length(txt)>1){"s"}else{""}
stop("unknown argument",txt.s,": \"",paste0(txt,collapse="\" \""),"\" \n")
}
if(is.null(parm)){
parm <- intersect(c("survival","cumhazard"),names(object))
}else if(any(parm %in% c("cumhazard","survival") == FALSE)){
txt <- parm[parm %in% c("cumhazard","survival") == FALSE]
txt2 <- paste0("\"",paste0(txt, collapse = "\" \""),"\"")
stop("Argument \'parm\' must be \"cumhazard\" or \"survival\" \n",
"incorrect value(s): ",txt2," \n")
}
if(any(parm %in% names(object) == FALSE)){
txt <- parm[parm %in% names(object) == FALSE]
txt2 <- paste0("\"",paste0(txt, collapse = "\" \""),"\"")
stop(txt2," has/have not been stored in the object \n",
"set argument \'parm\' to ",txt2," when calling predictCox \n")
}
if("cumhazard" %in% parm){
object$cumhazard.transform <- match.arg(cumhazard.transform, c("none","log"))
if(object$band[[1]] && is.null(object$cumhazard.se)){
stop("Cannot compute confidence bands \n",
"Set argument \'se\' to TRUE when calling predictCox \n")
}
if(object$band[[1]] && is.null(object$cumhazard.iid)){
stop("Cannot compute confidence bands \n",
"Set argument \'iid\' to TRUE when calling predictCox \n")
}
}
if("survival" %in% parm){
object$survival.transform <- match.arg(survival.transform, c("none","log","loglog","cloglog"))
if(object$band[[1]] && is.null(object$survival.se)){
stop("Cannot compute confidence bands \n",
"Set argument \'se\' to TRUE when calling predictCox \n")
}
if(object$band[[1]] && is.null(object$survival.iid)){
stop("Cannot compute confidence bands \n",
"Set argument \'iid\' to TRUE when calling predictCox \n")
}
}
## ** compute se, CI/CB
for(iType in parm){
if(iType=="cumhazard"){
min.value <- switch(object$cumhazard.transform,
"none" = 0,
"log" = NULL)
max.value <- NULL
}else if(iType=="survival"){
min.value <- switch(object$survival.transform,
"none" = 0,
"log" = NULL,
"loglog" = NULL,
"cloglog" = NULL)
max.value <- switch(object$survival.transform,
"none" = 1,
"log" = 1,
"loglog" = NULL,
"cloglog" = NULL)
}
outCIBP <- transformCIBP(estimate = object[[iType]],
se = object[[paste0(iType,".se")]],
iid = object[[paste0(iType,".iid")]],
null = NA,
conf.level = level,
nsim.band = nsim.band,
seed = seed,
type = object[[paste0(iType,".transform")]],
min.value = min.value,
max.value = max.value,
ci = object$se,
band = object$band,
p.value = FALSE)
names(outCIBP) <- paste0(iType,".", names(outCIBP))
object[names(outCIBP)] <- outCIBP
}
## ** export
object$conf.level <- level
return(object)
}
######################################################################
### confint.predictCox.R ends here
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