This is my first time to use R. 

For clarification:

I made an oa design for 4 factors with the following levels: one with 4 levels, 2 with 3 levels, 1  with 6 levels. 
Using DoE package, I have generated 72 runs (setting the columns="min3"). However, the numbers of generalized words of lengths 3 and 4 is still equal to 2.000000e+00 and 4.559372e-33, respectively. 
I am concerned that these will affect my estimates since my study is only interested in obtaining the orthogonal main effects of the factors.

How can I improve my design so that I can be ensured of the main effects?

Thank you very much.

Jonson M. Javier 
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