optmatch | R Documentation |

The results of a call to `groupmatch`

inherit all the features of
objects matched using `optmatch`

as described below.

The `optmatch`

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

or `pairmatch`

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

.

`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, `groupmatch`

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 `groupmatch`

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

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

and `summary.optmatch`

.)

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