reads and filters the identify_founders.tab file appropriately for analysis; returns a matrix with possibly-multiple rows per ptid (so rownames are non-unique)
reads and filters the identify_founders.tab file appropriately for analysis; returns a matrix with possibly-multiple rows per ptid (so rownames are non-unique)

pedlefsen/hiv-founder-id,pedlefsen/hiv-founder-id,pedlefsen/hiv-founder-id