A utility function to find observations that appear to violate support conditions. This function is not called anywhere in the code, but it is just useful for debugging some common issues that users run into.
trimmer(
g,
tname,
idname,
gname,
xformla,
data,
control_group = "notyettreated",
threshold = 0.999
)is a particular group (below I pass in 2009)
The name of the column containing the time periods
The individual (cross-sectional unit) id name
The name of the variable in data that
contains the first period when a particular observation is treated.
This should be a positive number for all observations in treated groups.
It defines which "group" a unit belongs to. It should be 0 for units
in the untreated group.
A formula for the covariates to include in the
model. It should be of the form ~ X1 + X2. Default
is NULL which is equivalent to xformla=~1. This is
used to create a matrix of covariates which is then passed
to the 2x2 DID estimator chosen in est_method.
The name of the data.frame that contains the data
Which units to use the control group.
The default is "nevertreated" which sets the control group
to be the group of units that never participate in the
treatment. This group does not change across groups or
time periods. The other option is to set
group="notyettreated". In this case, the control group
is set to the group of units that have not yet participated
in the treatment in that time period. This includes all
never treated units, but it includes additional units that
eventually participate in the treatment, but have not
participated yet.
the cutoff for which observations are flagged as likely violators of the support condition.
list of ids of observations that likely violate support conditions