# NOT RUN {
## Model with two correlated terms
m <- Shipley.Growth[[3]]
VIF(m) # Date & DD somewhat correlated
VIF(update(m, . ~ . - DD)) # drop DD
## Model with different types of predictor (some multi-coefficient terms)
d <- data.frame(
y = rnorm(100),
x1 = poly(rnorm(100), 2), # polynomial
x2 = as.factor(rep(c("a", "b", "c", "d"), each = 25)), # categorical
x3 = rep(1, 100) # no variation
)
m <- lm(y ~ x1.1 + x1.2 + x2 + x3, data = d)
VIF(m)
# }
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