optmatch | R Documentation |

The `optmatch`

class describes the results of an optimal full matching
(using either `fullmatch`

or `pairmatch`

). For the
most part, these objects can be treated as `factors`

.

The summary function quantifies `optmatch`

objects on the effective sample
size, the distribution of distances between matched units, and how well the
match reduces average differences.

```
## S3 method for class 'optmatch'
summary(
object,
propensity.model = NULL,
...,
min.controls = 0.2,
max.controls = 5,
quantiles = c(0, 0.5, 0.95, 1)
)
```

`object` |
The |

`propensity.model` |
An optional propensity model (the result of
a call to |

`...` |
Additional arguments to pass to |

`min.controls` |
To minimize the the display of a groups with many treated and few controls, all groups with more than 5 treated units will be summarized as “5+”. This is the reciprocal of the default value (1/5 = 0.2). Lower this value to see more groups. |

`max.controls` |
Like |

`quantiles` |
A points in the ECDF at which the distances between units will be displayed. |

`optmatch`

objects descend from `factor`

.
Elements of this vector correspond to members of the treatment and control
groups in reference to which the matching problem was posed, and are named
accordingly; the names are taken from the row and column names of
`distance`

. Each element of the vector is either `NA`

, indicating
unavailability of any suitable matches for that element, or the
concatenation of: (i) a character abbreviation of the name of the subclass
(as encoded using `exactMatch`

) (ii) the string `.`

; and
(iii) a non-negative integer. In this last place, positive whole numbers
indicate placement of the unit into a matched set and `NA`

indicates
that all or part of the matching problem given to `fullmatch`

was found
to be infeasible. The functions `matched`

,
`unmatched`

, and `matchfailed`

distinguish these
scenarios.

Secondarily, `fullmatch`

returns various data about the matching
process and its result, stored as attributes of the named vector which is
its primary output. In particular, the `exceedances`

attribute gives
upper bounds, not necessarily sharp, for the amount by which the sum of
distances between matched units in the result of `fullmatch`

exceeds
the least possible sum of distances between matched units in a feasible
solution to the matching problem given to `fullmatch`

. (Such a bound
is also printed by `print.optmatch`

and `summary.optmatch`

.)

`optmatch.summary`

`print.optmatch`

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