0x0 matrix.
3x3 matrix.
Remove values within distance 5 from zero:
col 0: locations 0 to -1
col 1: locations 0 to 0
1 : 6
col 2: locations 1 to 2
2 : 7
1 : -14
col 3: locations 3 to 2
Remove values within distance 20 from zero:
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.
