| ## tests of offsets, and prediction from them. |
| |
| load("anorexia.rda") # copied from package MASS |
| |
| ## via formula |
| fit1 <- lm(Postwt ~ Prewt + Treat + offset(Prewt), data = anorexia) |
| summary(fit1) |
| pred <- fitted(fit1) |
| stopifnot(all.equal(predict(fit1, anorexia), pred)) |
| |
| ## via argument |
| fit2 <- lm(Postwt ~ Prewt + Treat, data = anorexia, offset=Prewt) |
| summary(fit2) |
| stopifnot(all.equal(predict(fit2, anorexia), pred)) |
| |
| ## now spili into two parts |
| anorexia$o1 <- 0.9*anorexia$Prewt |
| anorexia$o2 <- 0.1*anorexia$Prewt |
| fit3 <- lm(Postwt ~ Prewt + Treat + offset(o1) + offset(o2), data = anorexia) |
| summary(fit3) |
| stopifnot(all.equal(predict(fit3, anorexia), pred)) |
| |
| fit4 <- lm(Postwt ~ Prewt + Treat + offset(o1), data = anorexia, offset = o2) |
| summary(fit4) |
| stopifnot(all.equal(predict(fit4, anorexia), pred)) |
| |
| ## using more than one offset failed in R 2.8.1 |
