# Predictions

## 1 R implementation for https://pclambert.net/software/stpm2/stpm2_timevar/

    library(rstpm2)
    library(readstata13)
    suppressWarnings(rott2b <- read.dta13("https://www.pclambert.net/data/rott2b.dta"))
    rott2b <- transform(rott2b, time = pmin(rf,60)/12)
    rott2b <- transform(rott2b, event = (rfi==1) & (time < 60/12))
    fit <- stpm2(Surv(time,event) ~ hormon + nsx(age,df=3,centre=60,stata=TRUE) + pr_1,
                 data=rott2b, df=4, stata=TRUE)
    eform(fit)

    Profiling...

                                                    exp(beta)        2.5 %       97.5 %
    (Intercept)                                  6.055607e-04 5.715701e-04 6.402896e-04
    hormonyes                                    1.253597e+00 1.065865e+00 1.462097e+00
    nsx(age, df = 3, centre = 60, stata = TRUE)1 6.550003e-01 5.594371e-01 7.702334e-01
    nsx(age, df = 3, centre = 60, stata = TRUE)2 3.449221e-01 1.993938e-01 5.962187e-01
    nsx(age, df = 3, centre = 60, stata = TRUE)3 9.626652e-01 7.189637e-01 1.275743e+00
    pr_1                                         9.080228e-01 8.944134e-01 9.214805e-01
    nsx(log(time), df = 4)1                      4.474345e+02 4.148646e+02 4.799754e+02
    nsx(log(time), df = 4)2                      1.974220e+02 1.894423e+02 2.047062e+02
    nsx(log(time), df = 4)3                      5.391834e+04 4.862060e+04 5.986957e+04
    nsx(log(time), df = 4)4                      7.282589e+01 6.949526e+01 7.650186e+01

    nd <- data.frame(age=60, hormon="no", pr_1=0)
    plot(fit, type="surv", newdata=nd, xlab="Years from surgery")

    library(ggplot2)
    nd <- data.frame(age=60, hormon=c("no","yes"), pr_1=0)
    haz <- predict(fit, type="haz", newdata=nd, grid=TRUE, se.fit=TRUE, keep=TRUE)
    haz <- cbind(haz,attr(haz,"newdata"))
    ggplot(haz, aes(time,group=hormon)) + geom_line(aes(y=Estimate,colour=hormon)) + geom_ribbon(aes(ymin=lower,ymax=upper), alpha=0.2) + xlab("Time since surgery (years)") + ylab("Hazard")

    s_time1 <- predict(fit, newdata=transform(rott2b, time=1), type="surv")
    hist(s_time1,xlab="Time from surgery",main="")

    s_time5 <- predict(fit, newdata=transform(rott2b, time=5), type="surv")
    hist(s_time5,xlab="Time from surgery",main="")

    library(ggplot2)
    nd <- with(rott2b, data.frame(age=seq(min(age), max(age), length=301), hormon="no", pr_1=3.43, time=1))
    s <- cbind(nd,predict(fit, newdata=nd, type="surv", se.fit=TRUE))
    ggplot(s,aes(age)) + geom_line(aes(y=Estimate)) + geom_ribbon(aes(ymin=lower,ymax=upper),alpha=0.2) +
        xlab("Age (years)") + ylab("Survival")

    s <- cbind(nd,predict(fit, newdata=transform(nd,time=5), type="surv", se.fit=TRUE))
    ggplot(s,aes(age)) + geom_line(aes(y=Estimate)) + geom_ribbon(aes(ymin=lower,ymax=upper),alpha=0.2) +
        xlab("Age (years)") + ylab("Survival")

Author: Mark Clements

Created: 2018-08-03 Fri 10:35

Validate