Logit implements UnivariateDifferentiableFunction, DifferentiableUnivariateFunction { @Deprecated public UnivariateFunction derivative() { return FunctionUtils.toDifferentiableUnivariateFunction(this).derivative(); } Logit();  Logit(double lo,
                 double hi); double value(double x); @Deprecated UnivariateFunction derivative(); DerivativeStructure value(final DerivativeStructure t);  }
@Test public void testDerivative() { final double lo = 1; final double hi = 2; final Logit f = new Logit(lo, hi); final DerivativeStructure f15 = f.value(new DerivativeStructure(1, 1, 0, 1.5)); Assert.assertEquals(4, f15.getPartialDerivative(1), EPS); }