Table 1. An example of the CKSAAP encoding scheme with k = 0, 1, 2, 3 for sequence fragment AAACD.

K	k-space amino acid pairs	The corresponding feature vectors
0	(AA, AC, AD,…,OO)441	(2, 1, 0,…,0)441
1	(AXA, AXC, AXD,…,OXO)441	(1, 1, 1,…,0)441
2	(AXXA, AXXC, AXXD,…,OXXO)441	(0, 1, 1,…,0)441
3	(AXXXA, AXXXC, AXXXD,…,OXXXO)441	(0, 0, 1,…,0)441