0x0 matrix.
3x3 matrix.
Remove row 0, column 1, and values above 6:
col 0: locations 0 to 0
3 : 1
col 1: locations 1 to 0
col 2: locations 1 to 1
1 : 4
col 3: locations 2 to 1
Remove everything:
col 0: locations 0 to -1
col 1: locations 0 to -1
col 2: locations 0 to -1
col 3: locations 0 to -1
uncompressed matrix.