Hello everyone,
 
I am trying to calculate predicted values for a fit from rq (quantreg; see
my earlier post), but I am having trouble understanding how to interpret the
coefficents in the summary.rq table generated by contr.poly.  This probably
applies equally to lm objects as well.
 
I've checked in Crawley's and Dalgaard's extremely helpful books, where I
found clear explanations of how to interpret the results of contr.treatment
and the others.  Can someone recommend a place to look for an equally simple
explanation of contr.poly?
 
Also, what is the advantage of using contr.poly over contr.treatment for
ordered factors?  Is it improper to use contr.treatment for ordered factors?
 
Many thanks in advance,
 
Sincerely,
 
Matt
 
R. Matthew Landis, Ph.D.
Dept. Biology
Middlebury College
Middlebury VT 05753
 
tel. 802/443.3484
fax.802/443.2072
 

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