40 lines
1.2 KiB
R
40 lines
1.2 KiB
R
|
## 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 split 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
|
||
|
|
|
||
|
|
|
||
|
|
## Using variable a name starting with "(weights)" :
|
||
|
|
anoD <- within(anorexia, `(weights)_2` <- Prewt)
|
||
|
|
fit5 <- lm(Postwt ~ `(weights)_2` + Treat + offset(o1) + offset(o2), data = anoD)
|
||
|
|
summary(fit5)
|
||
|
|
stopifnot(exprs = {
|
||
|
|
all.equal(predict(fit5, anoD), pred)
|
||
|
|
all.equal(sigma(fit5), sigma(fit1))
|
||
|
|
is.null(model.weights(model.frame(fit5)))
|
||
|
|
})
|
||
|
|
## these were all (even the model fit!) wrong in R <= 4.2.1
|