x |
data frame: left table
|
y |
data frame: right table
|
by |
character vector or variables to join by
|
copy |
If x and y are not from the same data source,
and copy is TRUE , then y will be copied into the
same src as x . This allows you to join tables across srcs, but
it is a potentially expensive operation so you must opt into it.
|
keep |
Should the join keys from both x and y be preserved in the
output?
If NULL , the default, joins on equality retain only the keys from x ,
while joins on inequality retain the keys from both inputs.
If TRUE , all keys from both inputs are retained.
If FALSE , only keys from x are retained. For right and full joins,
the data in key columns corresponding to rows that only exist in y are
merged into the key columns from x . Can't be used when joining on
inequality conditions.
|
suffix |
If there are non-joined duplicate variables in x and
y , these suffixes will be added to the output to disambiguate them.
Should be a character vector of length 2.
|
na_matches |
Should two NA or two NaN values match?
-
"na" , the default, treats two NA or two NaN values as equal, like
%in% , match() , and merge() .
-
"never" treats two NA or two NaN values as different, and will
never match them together or to any other values. This is similar to joins
for database sources and to base::merge(incomparables = NA) .
|
multiple |
Handling of rows in x with multiple matches in y .
For each row of x :
-
"all" , the default, returns every match detected in y . This is the
same behavior as SQL.
-
"any" returns one match detected in y , with no guarantees on which
match will be returned. It is often faster than "first" and "last"
if you just need to detect if there is at least one match.
-
"first" returns the first match detected in y .
-
"last" returns the last match detected in y .
|
relationship |
Handling of the expected relationship between the keys of
x and y . If the expectations chosen from the list below are
invalidated, an error is thrown.
-
NULL , the default, doesn't expect there to be any relationship between
x and y . However, for equality joins it will check for a many-to-many
relationship (which is typically unexpected) and will warn if one occurs,
encouraging you to either take a closer look at your inputs or make this
relationship explicit by specifying "many-to-many" .
See the Many-to-many relationships section for more details.
-
"one-to-one" expects:
-
"one-to-many" expects:
-
"many-to-one" expects:
-
"many-to-many" doesn't perform any relationship checks, but is provided
to allow you to be explicit about this relationship if you know it
exists.
relationship doesn't handle cases where there are zero matches. For that,
see unmatched .
|
reportvar |
character: Name of reporting variable. Default is ".joyn".
This is the same as variable "_merge" in Stata after performing a merge. If
FALSE or NULL, the reporting variable will be excluded from the final
table, though a summary of the join will be display after concluding.
|