[R] help with contrasts.

[Rodrigo Gazaffi]

Hello list,

I would like to know how can I use contrats in statistical analysis. I
have a simple model, "one-way analysis of variance" "or two-way..."
(balanced case).

I've already used the command aov (model) to get  the analysis of
variance, but i know that my treatment could be organized in groups,
so i would like to test these groups.

Example: I have 4 treatments t1, t2, t3, t4 and i would like to test
(1, 1, -1, -1) and (1, -1, 0, 0) and (0, 0, 1, -1).

thanks for the attention.

Rodrigo Gazaffi