Types of hierarchical joins — join

The basic join types used in the hmatch package ("left", "inner", "anti") are conceptually equivalent to dplyr's join types.

For each of the three join types there is also a counterpart prefixed by "resolve_" ("resolve_left", "resolve_inner", "resolve_anti"). In a resolve join rows of raw with matches to multiple rows of ref are resolved either to a single best match or no match before the subsequent join type is implemented. In a resolve join, rows of raw are never duplicated.

The exact details of match resolution vary somewhat among functions, and are explained within each function's documentation.

Value

left: return all rows from raw, and all columns from raw and ref. Rows in raw with no match in ref will have NA values in the new columns taken from ref. If there are multiple matches between raw and ref, all combinations of the matches are returned.
inner: return only the rows of raw that have matches in ref, and all columns from raw and ref. If there are multiple matches between raw and ref, all combinations of the matches are returned.
anti: return all rows from raw where there are not matches in ref, keeping just columns from raw
resolve_left: similar to "left", except that any row of raw that initially has multiple matches to ref is resolved to either a single 'best' match or no match. All rows of raw are returned, and rows of raw are never duplicated.
resolve_inner: similar to "inner", except that any row of raw that initially has multiple matches to ref is resolved to either a single 'best' match or no match. Only the rows of raw that can be resolved to a single best match are returned, and rows of raw are never duplicated.
resolve_anti: similar to "anti", except that any row of raw that initially has multiple matches to ref is considered non-matching (along with rows of raw that initially have no matches to ref), and returned as a single row. Rows of raw are never duplicated.