Page 359 - Applied Statistics with R

14.2. PREDICTOR TRANSFORMATION 359

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mpg Residuals 0
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hp Fitted

mpg_hp_log = lm(mpg ~ hp + I(hp ^ 2), data = autompg)
par(mfrow = c(1, 2))

plot(mpg ~ hp, data = autompg, col = "dodgerblue", pch = 20, cex = 1.5)
xplot = seq(min(autompg$hp), max(autompg$hp), by = 0.1)
lines(xplot, predict(mpg_hp_log, newdata = data.frame(hp = xplot)),
col = "darkorange", lwd = 2, lty = 1)

plot(fitted(mpg_hp_log), resid(mpg_hp_log), col = "dodgerblue",
pch = 20, cex = 1.5, xlab = "Fitted", ylab = "Residuals")
abline(h = 0, lty = 2, col = "darkorange", lwd = 2)

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mpg Residuals 0

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hp Fitted