I am fitting a regression model with a bs term and then making predictions
based on the model. According to some info on the internet at
http://www.stat.auckland.ac.nz/~yee/smartpred/DummiesGuide.txt
there are some problems with using predict.lm when you have a model with
terms such as bs,ns,or poly. However when I used one of the examples they
said would illustrate the problems I get virtually the same results using
the standard predict function and "safe prediction" method they propose. Has
lm been updated so that it can handle terms such as bs,ns, and poly
automatically? I am using R 2.3.0
this is their example:
n <- 100
set.seed(86) # For reproducibility of the random numbers
x <- sort(runif(n))
y <- sort(runif(n))
fit <- lm(y ~ bs(x, df=5))
plot(x, y,col="blue")
lines(x, fitted(fit), col="black")
newx <- seq(0, 1, len=n)
points(newx, predict(fit, data.frame(x=newx)), type="l", col=red, err=-1)
thanks,
Spencer
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