R Under development (unstable) (2026-01-18 r89306 ucrt) -- "Unsuffered Consequences"
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> x1 <- c(rep(0, 5), 1,1,1, 20, 40, 20, 1, 1, 1, rep(0, 5))
> x2 <- c(rep(0, 6), 1,1,1, 20, 40, 20, 1, 1, 1, rep(0, 4))
> time <- 1:length(x1)
> library(ptw)
> w1b <- ptw(ref = x1, samp = x2, mode = "backward")
> x2wb <- predict(w1b, x2, what = "response")
> stopifnot(sum(abs(x2wb - w1b$warped.sample), na.rm = TRUE) < 1E-8)
> t2wb <- as.numeric(predict(w1b, time, what = "time"))
> stopifnot(sum(abs(tail(t2wb, -1) - head(time, -1)), na.rm = TRUE) < 0.05)
> 
> w1f <- ptw(ref = x1, samp = x2, mode = "forward")
> x2wf <- predict(w1f, x2, what = "response")
> stopifnot(sum(abs(x2wf - w1f$warped.sample), na.rm = TRUE) < 1E-8)
> t2wf <- as.numeric(predict(w1f, time, what = "time"))
> stopifnot(sum(abs(tail(t2wf, -1) - head(time, -1)), na.rm = TRUE) < 0.05)
> 
> 
> proc.time()
   user  system elapsed 
   0.25    0.06    0.29