Hi, can someone please show me how to keep the coefficient as a new variable?

stk_return is the monthly firm return, mkt_return is the monthly market return. I'd like to run regressions for each firm and year and keep the coefficient as a new variable. E.g. For firm 1 in 1991: reg stk_return mkt_return

Thanks in advance

My data is like the following:
Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long stkcd double(year month stk_return mkt_return Monthlyrf)
1 1991  4        .  .015013 .0069299999999999995
1 1991  5 -.122253  .106617  .006091999999999999
1 1991  6 -.113459  .202348  .006091999999999999
1 1991  7 -.130921  .144743  .006091999999999999
1 1991  8 -.411588  .234801  .006091999999999999
1 1991  9 -.033333  .126685  .006091999999999999
1 1991 10  .855172  .208517  .006091999999999999
1 1991 11  .022305  .179662  .006091999999999999
1 1991 12  .067273  .193024  .006091999999999999
1 1992  1  .061329  .117241  .006091999999999999
1 1992  2  .012841  .127439  .006091999999999999
1 1992  3  .246049  .109534  .006091999999999999
1 1992  4  .477927  -.00677  .006091999999999999
1 1992  5  .174026 2.027975  .006091999999999999
1 1992  6 -.070796 -.215253  .006091999999999999
1 1992  7  .085714 -.074841  .006091999999999999
1 1992  8 -.095395 -.187555  .006091999999999999
1 1992  9  .081212 -.148286  .006091999999999999
1 1992 10  -.10426 -.242838  .006091999999999999
1 1992 11 -.041302  .372036  .006091999999999999
1 1992 12   .16188  .206037  .006091999999999999
1 1993  1  .098876  .690656  .006091999999999999
1 1993  2  .202454  .115085  .006091999999999999
1 1993  3  -.02381 -.335466  .006091999999999999
1 1993  4   .02439  .259627  .006091999999999999
1 1993  5 -.057181 -.312005  .006091999999999999
1 1993  6 -.079038   .08808              .007346
1 1993  7  -.08209 -.194005              .007346
1 1993  8 -.038618  .019601              .008719
1 1993  9 -.044397 -.009539              .008719
1 1993 10 -.033186 -.085627              .008719
1 1993 11  .016018  .207882              .008719
1 1993 12  .006757 -.165163              .008719
1 1994  1 -.192394  -.06143              .008719
1 1994  2   .00554  -.01819              .008719
1 1994  3 -.170799 -.068364              .008719
1 1994  4  .062458 -.165022              .008719
1 1994  5 -.086929 -.073285              .008719
1 1994  6 -.079452  -.15894              .008719
1 1994  7 -.047327 -.311451              .008719
1 1994  8    .5625 1.455937              .008719
1 1994  9     .152  .012342              .008719
1 1994 10 -.222222 -.181018              .008719
1 1994 11        0  .054312              .008719
1 1994 12 -.064286  -.05686              .008719
1 1995  1  .005725 -.132424              .008719
1 1995  2  .008539  -.02746              .008719
1 1995  3   .01223  .185929              .008719
1 1995  4 -.099442  -.09866              .008719
1 1995  5  .011352  .224136              .008719
1 1995  6 -.064286 -.098167              .008719
1 1995  7 -.003272  .105173              .008719
1 1995  8  .056893  .044884              .008719
1 1995  9  .009703 -.001915              .008719
1 1995 10 -.059645  .003425              .008719
1 1995 11 -.055331 -.105864              .008719
1 1995 12 -.081429 -.132706              .008719
1 1996  1 -.048212 -.036151              .008719
1 1996  2  .204248  .029457              .008719
1 1996  3  .077341  .009966              .008719
1 1996  4  .952141  .233917              .008719
1 1996  5  .580645 -.052523              .007346
1 1996  6  .249796  .272179              .007346
1 1996  7  .031352  .024752              .007346
1 1996  8  .036732   -.0168              .007346
1 1996  9 -.004887  .086782              .006022
1 1996 10  .065071  .113972              .006022
1 1996 11   .04438  .051437              .006022
1 1996 12   -.0883 -.122832              .006022
1 1997  1  .164649  .050773              .006022
1 1997  2 -.002079  .081001              .006022
1 1997  3  .421875  .187734              .006022
1 1997  4  .346154  .126726              .006022
1 1997  5 -.084626 -.081282              .006022
1 1997  6  .121879  -.02502              .006022
1 1997  7 -.080816 -.044272              .006022
1 1997  8 -.036156  .018442              .006022
1 1997  9 -.038357 -.104225              .006022
1 1997 10  .177382   .08509              .006022
1 1997 11 -.033081 -.033641              .004606
1 1997 12 -.064303  .046388              .004606
1 1998  1  .021145  .028097              .004606
1 1998  2 -.020276 -.017945              .004606
1 1998  3 -.050198  .033606              .004606
1 1998  4 -.032916  .084928              .004249
1 1998  5 -.037872  .052847              .004249
1 1998  6 -.146986 -.047729              .004249
1 1998  7  .008178 -.013481              .003891
1 1998  8  -.06489 -.125467              .003891
1 1998  9 -.022924  .079879              .003891
1 1998 10 -.055802 -.020841              .003891
1 1998 11  .065816  .027592              .003891
1 1998 12 -.056081 -.081189              .003891
1 1999  1 -.034045 -.009364              .003097
1 1999  2 -.060815 -.039364              .003097
1 1999  3  .007358  .062039              .003097
1 1999  4 -.021183  -.03293              .003097
1 1999  5  .383582  .138613              .003097
1 1999  6  .485437  .320228              .003097
1 1999  7 -.197531 -.049785 .0018559999999999998
end