I am doing a logistic regression, and by accident I included a field
which has the 2digit abbreviation for all 50 states labeled "st".  I was
surprised to see that the glm did not come up with an error message but
instead appears to have automatically broken down this field into
individual fields (stAK and stAL).  Does R really know to turn all
categorical variables in binary dummy variables?  I have tried answering
the question on my own and have found:



When including categorical variables in a regression, the default in R
is to

set the first level as the base.  Is there an option to specify a
different

level as the base?



My next/same question is what does it mean to "set the first level as
the base" does this mean it turns each value into a unique binary
result?


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