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R Library: Contrast Coding Systems for categorical variables, says we can use orthogonal polynomial for ordered factor encoding which the levels are equally spaced.

I do not understand why (mathematically) and intuition behind it. Could anyone explain it to me?

Does polynomial encoding have any relationship with polynomial regression?

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  • $\begingroup$ It's saying it can be used for equally spaced ordinal variables like income and education. So basically for discretised continuous variable, so yes same as polynomial regression but with discretised data as factors $\endgroup$ – seanv507 Nov 9 '16 at 21:45