# [R] Paritioning of Interaction SS in ANOVA - Gomez and Gomez(1984) example

peter dalgaard pdalgd at gmail.com
Thu May 9 18:01:13 CEST 2013

```On May 9, 2013, at 13:58 , Lundrigan, Cyril wrote:

> Hello
> I'm a new user of R and I'm using Deducer as the interface but also
> making use of the command interface where necessary.  I'm trying to
> replicate Table 6.18 on page 262 in Statistical Procedures in
> Agricultural Research, by K. A. Gomez and A. A. Gomez. New York,
> Chichester, etc.: Wiley (1984).
> http://pdf.usaid.gov/pdf_docs/PNAAR208.pdf.  This example is highly
> relevant to the type of data we will be analyzing in our department but
> nobody here has experience doing partitioning of interactions with
> software.
>

(Did you _have_ to give us a 600 page book to download to look at one table??)

This was likely done manually, and the syntax therefore may be a bit idiosyncratic, but according to what I _think_ is going on, you could set up Ta, Tb,..., Te as vectors or matrices with specific contrasts and then replace the term T:P in the model by

(Ta+Tb+Tc+Td+Te):P

As far as I can tell,

Ta is a vector which is 1 when T=7, 0 elsewhere
Tb is 1 when T=8
Tc is 1 when T=2 or T=5
Td is 1 when T=2
Te is a matrix with three columns
one is 1 when T=3
one is 1 when T=4
one is 1 when T=6

(you can probably also do this via releveled versions of the T factor in which certain levels are combined.)

> I've managed to replicate all previous steps for that particular
> exercise up to this point. If I interpret the syntax correctly, the
> table is showing comparisons of specific treatment combinations within
> the time variable P. Is this the correct interpretation?  If so, I don't
> know how to achieve that with R.  I had initially used SYSTAT for this
> exercise and had sent the problem along to their support person and
> after a few days the response was that he did not understand the syntax
> and, thus, could not replicate the table results. Unfortunately, it's
> also one of the few Gomez and Gomez examples not covered in the
> "agridat" package. I was trying to do the partiioning with
> interactionMeans and testInteractions functions in phia package but made
> no headway.  Greatly appreciate any help or direction with this.
>
> Thanks!
>
>
>
>
> “This email and any attached files are intended for the sole use of the primary and copied addressee(s) and may contain privileged and/or confidential information. Any distribution, use or copying by any means of this information is strictly prohibited. If you received this email in error, please delete it immediately and notify the sender.”
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help