help imb
-------------------------------------------------------------------------------

Title

    cem -- Measure of (Im)balance for CEM

Syntax

        imb varlist [if] [in] [, options]


    options               Description
    -------------------------------------------------------------------------
      treatment(varname)  name of the treatment variable
      breaks(string)      method used to generate cutpoints
      miname(string)      filename root of the imputed datasets, if in
                            separate files
      misets(integer)     number of imputed datasets, if in separate files
      impvar(string)      name of imputed dataset variable, if in stack/flong
                            format
      useweights          should the cem_weights be use?

Description

    imb returns a number of measures of imbalance in covariates between
    treatment and control groups. A multivariate L1 distance, univariate L1
    distrances, difference in means and empirical quatiles difference are
    reported. The L1 measures are computed by coarsening the data according
    to breaks and comparing across the multivariate histogram. See Iacus,
    King and Porro (2008) for more details on this measure.

Arguments

        +------+
    ----+ Main +-------------------------------------------------------------

    varlist is a list of variables to be included as coviarates.

        +---------+
    ----+ Options +----------------------------------------------------------

    treatment(varname) sets the treatment variable used for the imbalance
        checks.

    breaks(string) sets the default automatic coarsening algorithm. If either
        cem or imb has been run and there is a r(L1_breaks) available, this
        will be the default. Otherwise, the default for this is "scott". It
        is not incredibly important which method is used here as long as it
        is consistent.

    miname(string) if the imputed datasets are in separate files, is the root
        of the filenames of the imputed dataset. They should be in the
        working directory. For example, if miname were "imputed", then the
        filenames should be "imputed1.dta","imputed2.dta" and so on.

    misets(integer) if the imputed datasets are in separate files, is the
        number of imputed datasets being used for matching.

    impvar(string) if the imputed data is stacked in one dataset (the Stata
        default), this is the name of the variable identifying to which
        imputation the observation belongs.


    useweights makes imb use the weights from the output of cem. This is
        useful for checking balance after running cem.


Saved Results

    Scalars   
      r(L1)           multivariate imbalance measure


    Matrices  
      r(imbal)        matrix of univariate imbalance measures


    Strings   
      r(L1_breaks)    break method used for L1 distance


References and Distribution

    cem is licensed under GLP2. For more information, see:
    http://gking.harvard.edu/cem/

    For a full reference on Coarsened Exact Matching, see:

    Stefano M. Iacus, Gary King, and Giuseppe Porro, "Matching for Causal
        Inference Without Balance Checking", copy at
        <http://gking.harvard.edu/files/abs/cem-abs.shtml>

    To report bugs or give comments, please contact Matthew Blackwell
    <blackwel@fas.harvard.edu>.