This is a brief discussion of how microsynth allows the user to aggregate
outcome variables (passed to match.out
or match.out.min
) over time, either
before or after matching, and how that can affect the workings of two other
arguments: period
and start.pre
.
microsynth will match treatment and control based on the variables passed to
match.out
and match.out.min
. But there are two different ways to input
parameters to match.out
, and they have different implications for how the
arguments work.
The simple way to pass variables to match.out is with a simple vector of
variable names (e.g., match.out=c("Y1", "Y2")
. A more complex way is to pass a
list, containing a set of vectors with named corresponding to variable names and
elements corresponding to instructions for how to aggregate those variables over
time before matching, e.g. match.out = list('Y1' = c(1, 3, 3), 'Y2'=
c(2,5,1))
. Under this specification, if the intervention occurs at time 10,
then matching will proceed across a) The value of Y1 at time 10; b) the sum of
Y1 across times 7, 8 and 9; c) the sum of Y1 across times 4, 5 and 6; e) The sum
of Y2 across times time 9 and 10; e) the sum of Y2 across times 4, 5, 6, 7, and
8; f) the value of Y2 at time 3.
The choice between the simple and the complex input method is important, and it alters how other arguments work.
period
specifies the granularity of the data used by microsynth. When provided
simple input from match.out (i.e., a vector of variable names), period
indicates that those variables should be aggregated into the duration equal to
the value of period
. E.g., if data are provided monthly and period=3
, then
variables will be aggregated to the year-quarter before matching. But when
provided complex input from match.out (i.e., a list of names and integers), then
the user has already manually specified how the variables should be aggregated
prior to matching; in this case, period
will only affect the appearance of
charts and how results are reported (but not the matching procedure).
start.pre
is also affected. When match.out is provided the simple input (a
vector of variable names), start.pre will identify the time of the beginning of
the pre-intervention data to be used for matching, plotting, and displaying
results. Data observed any time before the start.pre
will be ignored
entirely. If provided the complex (list) input, then start.pre
will merely
affect plotting behavior and suppress some of the results. But observations
before the start.pre
will still be used for matching.
In conclusion, passing a list to match.out
will lock into place the parameters
around the matching procedure; arguments such as period
and start.pre
will
only alter how results are reported and how charts are plotted. But when
match.out
is passed only variable names, then period
and start.pre
will
also govern the matching procedure.
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