Orthogonal polynomial ANOVA or polynomial regression?
On Mar 24, 2011, at 16:53 , Dominick Samperi wrote:
Hi, I have not been able to find R tools that permit an orthogonal polynomial ANOVA analysis: single degree of freedom F-test comparisons including L, Q, C, etc. terms. Do such tools exist? I guess you can accomplish something similar by doing straightforward polynomial regression and removing powers manually, combined with ANOVA model comparisons.
(Why R-devel? This is a plain R-help thing.) Look up contr.poly(), and poly(). Notice that for unbalanced designs, you still need to remove terms one at a time.
Peter Dalgaard Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com