[P] _ms_balance -- Adjust e(b) by balancing factor-variable covariates
_ms_balance [indepvars] [, zero strict]
_ms_balance is a programmer's command that makes an adjusted copy of e(b)
by balancing the specified factor-variable covariates in its column
stripe. The column names in the adjusted copy of e(b) will no longer
refer to the variables in indepvars, and elements that referenced these
variables will have been multiplied by a fraction representing a
balancing of the levels of the factors in indepvars.
zero specifies that empty cells be treated as true zero estimates with
zero variance. This results in a multiplier of 1/k for each factor
variable in indepvars, where k is the number of levels for a given
factor variable in indepvars. Interactions containing multiple
variables in indepvars will be adjusted by the multiplier from each
participating factor variable.
By default, _ms_balance uses a multiplier that ignores empty cells.
An interaction with k levels and e empty cells will have a multiplier
of 1/(k-e) if all its factor variables are in indepvars. Otherwise,
the multiplier is determined by the number of nonempty cells for each
level-combination of factor variables not in indepvars.
strict specifies that an error be raised if there are any empty cells
involving the factor variables in indepvars.
_ms_balance stores the following in r():
r(b) adjusted copy of e(b)
r(mult) row vector of the multipliers associated with each element
of the original e(b)