The mysterious .L, .Q., and .C

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Ok, I know this is dumb of me (obviously), but I bet I am not the only one ever who wondered what those mysterious x.L, x.Q., and x.C variables are that R automatically creates when an ordered factor x is entered into a model (lm, glm, lmer, etc.).  Well, it should be kinda obvious, but with enough whiskey those things can stand for anything.

Anyway, on the odd chance that somebody will google for those terms and look for salvation: The default coding R uses for ordered predictors is simply polynomial contrast coding … (Linear, Quadratic, Cubic, etc.) .

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2 thoughts on “The mysterious .L, .Q., and .C

    Austin Frank said:
    February 16, 2008 at 11:18 pm

    Never any credit to the grad students who have to explain these things to you…

    Like

    tiflo said:
    February 25, 2008 at 3:45 pm

    damn it. you’re right. you told me this once, right. and then i forgot about it and rediscovered it. genius me. oh man, this is worse than i thought ;-). everyone: austin frank, the man who first told me about L-Q-C =)

    Like

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