> age <- c(23,19,25,10,9,12,11,8)
> steroid <- c(27.1,22.1,21.9,10.7,7.4,18.8,14.7,5.7)
> sample <- data.frame(age,steroid)
> fit2 <- lm(sample$steroid~poly(sample$age,2,raw=TRUE))
> fit2
Call:
lm(formula = sample$steroid ~ poly(sample$age, 2, raw = TRUE))
Coefficients:
(Intercept) -27.7225
poly(sample$age, 2, raw = TRUE)1 5.1819
poly(sample$age, 2, raw = TRUE)2 -0.1265
> (newdata=data.frame(age=15))
age
1 15
> predict(fit2,newdata,interval="predict")
fit lwr upr
1 24.558395 17.841337 31.27545
2 25.077825 17.945550 32.21010
3 22.781034 15.235782 30.32628
4 11.449490 5.130638 17.76834
5 8.670526 2.152853 15.18820
6 16.248596 9.708411 22.78878
7 13.975514 7.616779 20.33425
8 5.638620 -1.398279 12.67552
Warning message:
'newdata' had 1 rows but variable(s) found have 8 rows
predict
関数が age=15 を予測できないのはなぜですか?