8 ways to traverse a region

a0:b1 = { 1, 2, 3, 4}; print; print bycols;
plot a0:b1; plot b1:a0; plot b0:a1; plot a1:b0;
bycols;
plot a0:b1; plot b1:a0; plot b0:a1; plot a1:b0;

        A       B               0       1
0       1       2       A       1       3
1       3       4       B       2       4

        1       2               1       3
        3       4               2       4

        4       3               4       2
        2       1               3       1

        2       1               2       4
        4       3               1       3

        3       4               3       1
        1       2               4       2