Dear R People:

I have the following in a file:

resp factA factB
39.5 low B-
38.6 high B-
27.2 low B+
24.6 high B+
43.1 low B-
39.5 high B-
23.2 low B+
24.2 high B+
45.2 low B-
33.0 high B-
24.8 low B+
22.2 high B+

and I construct the data frame:

> collard.df <- read.table("collard.txt",header=TRUE)
> collard.aov <- aov(resp~factA*factB,data=collard.df)
> summary(collard.aov)
            Df Sum Sq Mean Sq F value   Pr(>F)
factA        1   36.4    36.4   5.511   0.0469 *
factB        1  716.1   716.1 108.419 6.27e-06 ***
factA:factB  1   13.0    13.0   1.971   0.1979
Residuals    8   52.8     6.6
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> tapply(collard.df$resp,list(collard.df$factA,collard.df$factB),mean)
           B-       B+
high 37.03333 23.66667
low  42.60000 25.06667
>

Fair enough.  Let's pretend for a second that interaction existed.  Then I
want to set up contrasts such that mean(high) - mean(low) = 0 and mean(B+)
- mean(B-)  = 0.

I know that this is really simple, but I've tried all kinds of things with
glht and am not sure that I'm on the right track.  Sorry for the trouble
for the simple question.

Thanks,
erin




-- 
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodgess@gmail.com

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