# Is it okay to combine dummy coding and sequence coding?

I have a model with two categorical variables. Each one has three levels. Iv1 has a natural reference category so I would like to use dummy coding, and compare level 2 to level 1, and level 3 to level 1. Iv2 is sequential and I would like to compare level 2 to level 1, and level 3 to level 2.

R automatically creates contrasts that then look like this:

For Iv1:

  i ii
1 0  0
2 1  0
3 0  1


For Iv2:

         i        ii
1 -0.6666667 -0.3333333
2  0.3333333 -0.3333333
3  0.3333333  0.6666667


Is there anything wrong with using these two kinds of contrasts, and including an interaction between them?