imbalance | R Documentation |

Calculates several imbalance measures for the original and matched data sets

imbalance(group, data, drop=NULL, breaks = NULL, weights, grouping = NULL)

`group` |
the group variable |

`data` |
the data |

`drop` |
a vector of variable names in the data frame to ignore |

`breaks` |
a list of vectors of cutpoints used to calculate the L1 measure. See Details. |

`weights` |
weights |

`grouping` |
named list, each element of which is a list of groupings for a single categorical variable. See Details. |

This function calculates several imbalance measures.
For numeric variables, the difference in means (under the column
`statistic`

), the difference in quantiles and the L1 measure is
calculated. For categorical variables the L1 measure and the
Chi-squared distance (under column `statistic`

) is calculated.
Column `type`

reports either `(diff)`

or `(Chi2)`

to
indicate the type of statistic being calculated.

If `breaks`

is not specified, the Scott automated bin calculation
is used (which coarsens less than Sturges, which used in
`cem`

). Please refer to `cem`

help page. In
this case, breaks are used to calculate the L1 measure.

This function also calculate the global L1 imbalance measure.
If `breaks`

is missing, the default rule to calculate cutpoints
is the Scott's rule.

The `grouping`

option is a list where each element is itself a
list. For example, suppose for variable `quest1`

you have the
following possible levels ```
"no answer", NA, "negative", "neutral",
"positive"
```

and you want to collect `("no answer", NA, "neutral")`

into a single group, then the `grouping`

argument should contain
`list(quest1=list(c("no answer", NA, "neutral")))`

. Or if you have
a discrete variable `elements`

with values `1:10`

and you want
to collect it into groups “`1:3,NA`

”, “`4`

”,
“`5:9`

”, “`10`

” you specify in `grouping`

the
following list `list(elements=list(c(1:3,NA), 5:9))`

. Values not
defined in the `grouping`

are left as they are. If `cutpoints`

and `groupings`

are defined for the same variable, the
`groupings`

take precedence and the corresponding cutpoints are set
to `NULL`

.

See `L1.meas`

help page for details.

An object of class `imbalance`

which is a list with the following
two elements

`tab` |
Table of imbalance measures |

`L1` |
The global L1 measure of imbalance |

Stefano Iacus, Gary King, and Giuseppe Porro

Iacus, King, Porro (2011) doi: 10.1198/jasa.2011.tm09599

Iacus, King, Porro (2012) doi: 10.1093/pan/mpr013

Iacus, King, Porro (2019) doi: 10.1017/pan.2018.29

data(LL) todrop <- c("treated","re78") imbalance(LL$treated, LL, drop=todrop) # cem match: automatic bin choice mat <- cem(treatment="treated", data=LL, drop="re78")

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