[R] simple main effect.

[Richard M. Heiberger]

For simple effects in the presence of interaction there are several
options included in the HH package.  If you don't already have the HH
package, you can get it with
   install.packages("HH")

Graphically, you can plot them with the function
   interaction2wt(..., simple=TRUE)
See the examples in
   ?HH::interaction2wt

For tests on the simple effect of A conditional on a level of B, you
can use the model formula B/A and look at the partition of the sums of
squares using the split= argument
   summary(mymodel.aov, split=<put your details here>)

For multiple comparisons from designs with Error() terms, you need to
specify the same sums of squares with an equivalent formula that doesn't 
use the Error() function.  See the maiz example in
   ?HH::MMC
Read the example all the way to the end of the help file.

Rich