pair {cem} | R Documentation |
Produces a paired sample out of a CEM match solution
pair(obj, data, method=NULL, mpower=2, verbose=0)
obj |
an object as output from cem |
data |
the original data.frame used by cem |
method |
distance method to use in k2k matching. See Details. |
mpower |
power of the Minkowski distance. See Details. |
verbose |
controls level of verbosity. Default=0. |
This function returns a vector of paired matched units index.
The user can choose a method
(between `euclidean
',
`maximum
', `manhattan
', `canberra
', `binary
'
and `minkowski
') for nearest neighbor matching inside each
cem
strata. By default method
is set to `NULL
',
which means random matching inside cem
strata. For the Minkowski
distance the power can be specified via the argument mpower
'.
For more information on method != NULL
, refer to
dist
help page.
obj |
a list with the fields paired , full.paired ,
reservoir and reservoir2 . The latter contain the indexes
of the unmatched units. |
Stefano Iacus, Gary King, and Giuseppe Porro
Stefano Iacus, Gary King, Giuseppe Porro, ``Matching for Casual Inference Without Balance Checking,'' http://gking.harvard.edu/files/abs/cem-abs.shtml
data(LL) # cem match: automatic bin choice mat <- cem(data=LL, drop="re78") # we want a set of paired units psample <- pair(mat, data=LL) table(psample$paired) psample$paired[1:100] table(psample$full.paired) psample$full.paired[1:10] # cem match: automatic bin choice, we drop one row from the data set mat1 <- cem(data=LL[-1,], drop="re78") # we want a set of paired units but we have an odd number of units in the data psample <- pair(mat1, data=LL[-1,]) table(psample$full.paired)