The format is:
logi [1:56, 1:250] FALSE FALSE FALSE FALSE FALSE FALSE ...
- attr(*, "dimnames")=List of 2
..$ : chr [1:56] "metformin" "phenformin" "phenyl biguanide" "estradiol" ...
..$ : chr [1:250] "-2147375257" "-2147119955" "-2146474760" "-2145840573" ...