Split matching type (one of "1:1", "m:1", "1:m", "m:m"
) into its two components
split_match_type(match_type)
character vector
character: one of "m:m", "m:1", "1:m", "1:1". Default is "1:1" since this the most restrictive. However, following Stata's recommendation, it is better to be explicit and use any of the other three match types (See details in match types sections).