# imbalance: Calculates several imbalance measures In cem: Coarsened Exact Matching

 imbalance R Documentation

## Calculates several imbalance measures

### Description

Calculates several imbalance measures for the original and matched data sets

### Usage

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

### Arguments

 `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.

### 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.

### Value

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

### Author(s)

Stefano Iacus, Gary King, and Giuseppe Porro

### References

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

### Examples

```

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")

```

cem documentation built on Sept. 8, 2022, 5:09 p.m.