Ordinal Ordinal Models derivative formula: derivative of ( w1 * ln(f(c1 - b*x)) + w2 * ln(f(c2 + c1 - b*x) - f(c1 - b*x)) + w3 * ln(f(c3 + c2 + c1 - b*x) - f(c2 + c1 - b*x)) + w4 * ln( - f(c3 + c2 + c1 - b*x)) ) wrt c2