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Forgive my resending this post. To data I have received only one response (thank you Bert Gunter), and I still do not have an answer to my question. Respectfully, John Windows XP R 2.12.1 contrast package. I am trying to understand how to create contrasts for a model that contatains an interaction. I can get contrasts to work for a model without interaction, but not after adding the interaction. Please see code below. The last two contrast statements show the problem. I would appreciate someone letting me know what is wrong with the syntax of my contrast statements. Thank you,...

Dear r-community, Today I have completed my PhD.  I would like to take this opportunity to thank the r-community for helping me with the r-coding.  I use r to do data manipulation during my PhD and I benefit a lot through the discussion in the r-forum. I will continue using R and help the others too. Thank you so much. Regards, Roslina UniSA. [[alternative HTML version deleted]]