27 lines
776 B
R
27 lines
776 B
R
library(survival)
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#
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# Check out intercept/interaction for Frank H
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#
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age2 <- lung$age - 50
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fit1 <- coxph(Surv(time, status) ~ age * strata(sex), lung)
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fit2 <- coxph(Surv(time, status) ~ age2*strata(sex), lung)
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tdata <- data.frame(age=50:60, age2=0:10, sex=c(1,2,1,2,1,2,1,2,1,2,1))
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surv1 <- survfit(fit1, tdata)
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surv2 <- survfit(fit2, tdata)
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# The call won't match, nor the newdata data frame
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icall <- match(c("newdata", "call"), names(surv1))
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all.equal(unclass(surv1)[-icall], unclass(surv2)[-icall])
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# It should match what I get with a single strata fit
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fit3 <- coxph(Surv(time, status) ~ age, data=lung,
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init=fit1$coef[1], subset=(sex==1), iter=0)
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surv1b <- survfit(fit3, newdata=list(age=c(50,52, 54)))
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all.equal(c(surv1b$surv), surv1[c(1,3,5)]$surv)
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