Re: [R] creating 'all' sum contrasts

2010-10-15 Thread Jonathan Christensen
Michael, Let c_1 and c_2 be vectors representing contrasts. Then c_1 and c_2 are orthogonal if and only if the inner product is 0. In your example, you have vectors (1,0,-1) and (0,1,-1). The inner product is 1, so they are not orthogonal. It's impossible to have more orthogonal contrasts than you

Re: [R] creating 'all' sum contrasts

2010-10-15 Thread Michael Hopkins
On 15 Oct 2010, at 13:55, Berwin A Turlach wrote: > G'day Michael, > Hi Berwin Thanks for the reply > On Fri, 15 Oct 2010 12:09:07 +0100 > Michael Hopkins wrote: > >> OK, my last question didn't get any replies so I am going to try and >> ask a different way. >> >> When I generate contrast

Re: [R] creating 'all' sum contrasts

2010-10-15 Thread Berwin A Turlach
G'day Michael, On Fri, 15 Oct 2010 12:09:07 +0100 Michael Hopkins wrote: > OK, my last question didn't get any replies so I am going to try and > ask a different way. > > When I generate contrasts with contr.sum() for a 3 level categorical > variable I get the 2 orthogonal contrasts: > > > con

[R] creating 'all' sum contrasts

2010-10-15 Thread Michael Hopkins
OK, my last question didn't get any replies so I am going to try and ask a different way. When I generate contrasts with contr.sum() for a 3 level categorical variable I get the 2 orthogonal contrasts: > contr.sum( c(1,2,3) ) [,1] [,2] 110 201 3 -1 -1 This provides the