fragilityindex (version 0.1.0)

survivalfragility: Survival Fragility Function

Description

Compute the fragility of a coefficient in a survival test, i.e. the number of removed observations it would take to make a significant-result non-significant. Uses the coxph() function from the survival package.

Usage

survivalfragility(formula, data, covariate = "all.factors.default",
  conf.level = 0.95, verbose = FALSE)

Arguments

formula

Model formula which will be evaluated by coxph()

data

Dataframe with values for model forma, passed to coxph()

covariate

Vector of covariates to find fragility index for. Default is all covariates in formula

conf.level

Significance level

verbose

Logical indicating if function will return verbose results or only fragility index

Value

If verbose is FALSE, returns a list with fragility indices for selected covariates. If verbose is TRUE, returns a list with p-values for each fragility index at each iteration of the algorithm.

Examples

# NOT RUN {
library(survival); data <- lung
data$status = lung$status - 1 # recode status as a 0/1 variable

survivalfragility(Surv(time, status) ~ pat.karno + strata(inst),
                  data, covariate = "pat.karno")

survivalfragility(Surv(time, status) ~ pat.karno + ph.karno + strata(inst),
                  data, verbose = TRUE)
                  #algorithm does not converge for strata(inst)

survivalfragility(Surv(time, status) ~ pat.karno + ph.karno + strata(inst),
                  data, covariate = c("pat.karno","ph.karno"))


# }