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是否可以使用虛擬變量檢查模型中的多重共線性?假設下面的例子當存在因素時測試多重共線性
treatment <- factor(rep(c(1, 2), c(43, 41)), levels = c(1, 2), labels = c("placebo", "treated"))
improved <- factor(rep(c(1, 2, 3, 1, 2, 3), c(29, 7, 7, 13, 7, 21)), levels = c(1, 2, 3), labels = c("none", "some", "marked"))
numberofdrugs <- rpois(84, 5)+1
healthvalue <- rpois(84,5)
y <- data.frame(healthvalue,numberofdrugs, treatment, improved)
test <- lm(healthvalue~numberofdrugs+treatment+improved, y)
什麼是我應該做的,當我要檢查,如果在這樣的模式出現多重?