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.

## Arguments

- object
The

`optmatch`

object to summarize.- propensity.model
An optional propensity model (the result of a call to

`glm`

) to use when summarizing the match. If the RItools package is installed, an additional chi-squared test will be performed on the average differences between treated and control units on each variable used in the model. See the`xBalance`

function in the RItools package for more details.- ...
Additional arguments to pass to

`xBalance`

when also passing a propensity model.- 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

`min.controls`

sets maximum group sized displayed with respect to the number of controls. Raise this value to see more groups.- quantiles
A points in the ECDF at which the distances between units will be displayed.

## Details

`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`

.)