[R] Trouble with contrasts

[Patrick E. McKnight]

Greetings,

I have a nagging problem with contrasts and I can't seem to resolve it. 
A factor exists with four levels (lib1, lib2, con1, con2) and when I
check the contrasts or set the contrasts to any of the prespecified
ones, I do not get the exact contrasts necessary to test the
theoretically relevant ones.  I need orthogonal contrasts that look just
like this matrix:

       con1   con2    con3
lib1     1      0       1
lib2    -1      0       1
con1     0      1      -1
con2     0     -1      -1

How might I change the contrast matrix for this factor and this one
alone?  I see in the documentation that C ought to be the ticket but I
can't figure out how to specify the matrix correctly.  I read in MASS or
S programming that the matrix can be specified but I was unable to
follow the example and apply the logic to my problem.

Thanks in advance for any help solving this problem.

-- 
________________________________________________________________________

Cheers,

Patrick
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