R version 4.4.0 beta (2024-04-15 r86425 ucrt) -- "Puppy Cup"
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> library(survival)
> options(na.action=na.exclude, contrasts=c('contr.treatment', 'contr.poly'))
> 
> # Verify stratified fits in a simple way, but combining two data
> #  sets and doing a single fit
> #
> aeq <- function(x,y) all.equal(as.vector(x), as.vector(y))
> 
> tdata <- data.frame(time=c(lung$time, ovarian$futime),
+                     status=c(lung$status-1, ovarian$fustat),
+                     group =rep(0:1, c(nrow(lung), nrow(ovarian))))
> fit1 <- survreg(Surv(time, status) ~ 1, lung)
> fit2 <- survreg(Surv(futime, fustat) ~ 1, ovarian)
> fit3 <- survreg(Surv(time, status) ~ group + strata(group), tdata)
> 
> aeq(c(fit1$coef, fit2$coef-fit1$coef), fit3$coef)
[1] TRUE
> aeq(c(fit1$scale, fit2$scale), fit3$scale)
[1] TRUE
> aeq(fit1$loglik[2] + fit2$loglik[2], fit3$loglik[2])
[1] TRUE
> 
> #
> # Test out the cluster term in survreg, which means first a test
> #  of the dfbeta residuals
> # I also am checking that missing values propogate
> test1 <- data.frame(time=  c(9, 3,1,1,6,6,8),
+                     status=c(1,NA,1,0,1,1,0),
+                     x=     c(0, 2,1,1,1,0,0),
+                     id=  1:7)
> fit1 <- survreg(Surv(time, status) ~ x, cluster = id, test1)
> fit2 <- survreg(Surv(time, status) ~ x + cluster(id), test1) #old form
> all.equal(fit1, fit2)
[1] TRUE
> 
> db1 <- resid(fit1, 'dfbeta')
> ijack <-db1
> eps <- 1e-7
> for (i in 1:7) {
+     temp <- rep(1.0,7)
+     temp[i] <- 1-eps
+     tfit <- survreg(Surv(time, status) ~ x, test1, weight=temp)
+     ijack[i,] <- c(tfit$coef, log(tfit$scale)) 
+     }
> ijack[2,] <- NA  # stick the NA back in
> ijack <- (rep(c(fit1$coef, log(fit1$scale)), each=nrow(db1)) - ijack)/eps
> all.equal(db1, ijack, tolerance=eps)
[1] TRUE
> all.equal(t(db1[-2,])%*% db1[-2,], fit1$var)
[1] TRUE
> 
> # This is a harder test since there are multiple strata and multiple 
> #  obs/subject.  Use of enum + strata(enum) in essenence fits a different
> #  baseline Weibull to each strata, with common coefficients for rx, size, and
> #  number.
> fit1 <- survreg(Surv(stop-start, event) ~  rx + size + number + 
+                 factor(enum) + strata(enum), data=bladder2)
> 
> db1 <- resid(fit1, type='dfbeta', collapse=bladder2$id)
> ijack <- db1  # a matrix of the same size
> for (i in 1:nrow(db1)) {
+     twt <- rep(1., nrow(bladder2))
+     twt[bladder2$id==i] <- 1-eps
+     tfit <- survreg(Surv(stop-start, event) ~ rx + size + number + 
+                     factor(enum) + strata(enum), data=bladder2, 
+                     weight=twt)
+     ijack[i,] <- c(coef(tfit), log(tfit$scale)) 
+     }
> ijack <- (rep(c(fit1$coef, log(fit1$scale)), each=nrow(db1)) - ijack)/eps
> all.equal(db1, ijack, tolerance=eps*2)
[1] TRUE
> 
> 
> proc.time()
   user  system elapsed 
   1.26    0.07    1.32