Polynomial Contrast in SAS and R

Calculation of Polynomial Contrast Coefficient is easy in equal spaced cases but not straigt forward in unequal sapced factors. They can be calculated using either SAS or R.  SAS would need the SAS/IML package. R is free, but it gives the raw decimal point results. To make it integer, you have to normalize yourself.

 

 Equal Spaced and Equal Sample Size

 

 Three Methods

 1.   Check any ANOVA textbook

 2.   In SAS, use orpol() function in SAS/IML

 3.   In R/S-plus,  use contr.poly()

 

 Unequal Spaced

 Two Methods

 1.  In SAS, use orpol() function in SAS/IML

 2.  In R/S-plus, use poly()