I have a dataset with 2 columns of ID numbers (id1 id2). Each row establishes a link between 2 ID numbers There are several many-to-many links, and some ID numbers appear in both columns. I want to create a "group-ID" for all IDs which are interlinked with each other. How can I do this? In the example below, I want to create 2 group IDs: one for ID numbers a b c d, and another for ID numbers e f. data have; input (id1 id2) (:$1.); cards; a b a c b d e f ; Thanks for your help. Karen
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