[R] Problems on testing moderating effect (or interactive effect).

[Jonathan Baron]

On 07/04/06 19:51, Guo Wei-Wei wrote:
> Can I use the variance-covariance matrix as the input data? Just like
> what SEM does. My mentor told me to avoid sperate the operation into
> two step, that is to get the factors' means first and then to test the
> relationships. I'm used to use sem package. I'm not familiar with
> lm(). I trid summary(lm(B ~ A*C)) and failed to get any result.
> 
> Can sem deal with mediation? And could you tell me the command of
> generating a interaction item of A (nxp) and C (mxp)?

I don't use sem, but I don't see why you need it for this.  This
is a simple regression problem, so far as I can tell.

I think you need to do some reading of the R documentation.  What
are A, B, and C?  They should be vectors.  That was the point of
my comment about rowMeans.

You seem to be guessing and relying on authority instead of
trying to understand.

-- 
Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page: http://www.sas.upenn.edu/~baron