Date	Level	SLOPE	CURVATURE	SLOPE	CURVATURE
9/26/2008	2.14%	3.64%	2.04%	1.57%
9/10/2008	2.40%	2.07%	0.59%	-0.06%
8/25/2008	2.51%	2.13%	0.63%	-0.09%
8/11/2008	2.69%	2.22%	0.78%	-0.19%
7/25/2008	2.75%	2.41%	1.05%	0.06%
7/10/2008	2.54%	2.35%	0.89%	-0.28%
6/25/2008	2.82%	2.63%	1.47%	0.52%
6/10/2008	2.92%	2.11%	0.97%	-

HOW CAN I CALCULE CURVATURE ?