bs {splines}

#require(stats); require(graphics)

bs(women$height, df = 5)

summary(fm1 <- lm(weight ~ bs(height, df = 5), data = women))

## example of safe prediction

plot(women, xlab = "Height (in)", ylab = "Weight (lb)")

ht <- seq(57, 73, length.out = 200)

lines(ht, predict(fm1, data.frame(height = ht)))