- ## number of boostrap replications nboot <- 10000 res <- lapply(seq_len(nboot), function(i) { index <- sample(unique(sir.cont$id), replace=TRUE) dboot <- sir.cont[unlist(sapply(index, function(x) which(x==sir.cont[["id"]] ))), ] coef01 <- coef(coxph(Surv(time, to == 1) ~ age + sex, dboot, subset = from == 0)) coef10 <- coef(coxph(Surv(time, to == 0) ~ age + sex, dboot, subset = from == 1)) matrix(c(coef01, coef10), ncol = 4) }) res <- do.call(rbind, res) se.boot <- matrix(sqrt(apply(res, 2, var)), ncol = 4, dimnames = list("", c("age01", "sex01", "age10", "sex10")))
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