Sigmoid implements UnivariateDifferentiableFunction, DifferentiableUnivariateFunction { @Deprecated public UnivariateFunction derivative() { return FunctionUtils.toDifferentiableUnivariateFunction(this).derivative(); } Sigmoid();  Sigmoid(double lo,
                   double hi); @Deprecated UnivariateFunction derivative(); double value(double x); DerivativeStructure value(final DerivativeStructure t);  }
@Test public void testDerivative() { final Sigmoid f = new Sigmoid(); final DerivativeStructure f0 = f.value(new DerivativeStructure(1, 1, 0, 0.0)); Assert.assertEquals(0.25, f0.getPartialDerivative(1), 0); }