Hello,
Using _b, I have no problem to access the coefficients of contrinuous vairables in a regression. As in the below example, I can easily generate a variable for weight. But I am not sure how to get the equivalent for each value of make. I imagine it is a simple problem and I am not putting in the right search terms. Below is the code/output.

Code:
. use http://www.stata-press.com/data/r13/auto2, clear
(1978 Automobile Data)
 
.
. encode(make), gen(nmake)
 
.
. qui: reg mpg weight i.nmake
 
.
. gen mpgcoef=_b[weight]
 
.
. di mpgcoef
-.02083333
 
. gen makecoeff=_b[i.nmake]
i:  operator invalid