R_分类变量构造虚拟变量

a <- factor(rep(letters[1:3], 2)) # 产生一个因子变量a ## [1] a b c a b c ## Levels: a b c a_dummy <- model.matrix(~factor(a) - 1) a_dummy <- as.data.frame(a_dummy) names(a_dummy) <- paste("a", 1:length(a_dum

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