Hi Franz,
you can take a look at the following class which is used for the unit tests:
public class QuinticFunction implements UnivariateDifferentiableFunction {
/* Evaluate quintic.
* @see org.apache.commons.math3.UnivariateFunction#value(double)
*/
public double value(double x) {
return (x-1)*(x-0.5)*x*(x+0.5)*(x+1);
}
public DerivativeStructure value(DerivativeStructure t) {
return
t.subtract(1).multiply(t.subtract(0.5)).multiply(t).multiply(t.add(0.5)).multiply(t.add(1));
}
}
The DerivativeStructure provides the standard arithmetic operations which
you can use.
So in your case the value method would look like this imho:
public DerivativeStructure value(DerivativeStructure t) {
return t.multiply(t);
}
This just a quick help from myside, Luc (Maisonobe) will surely give you
more infos on how to use the DerivativeStructure.
Thomas
On Tue, May 21, 2013 at 4:21 PM, Franz Simons <
[email protected]> wrote:
> Dear all,
>
> I don't understand the usage of the new DerivativeStructure in version 3
> of the commons math.
>
> In the old version I had the following function, which was then used in
> the Newton solver:
>
> public class MyFunction implements
> DifferentiableUnivariateRealFunction {
>
>
> public double value(double x) {
> // example value
> return x*x;
> }
>
> public UnivariateRealFunction derivative() {
> return new UnivariateRealFunction() {
> public double value(double x) {
> // example derivative
> return 2.*x;
> }
> }
> }
> }
>
> To use the Newton Raphson solver in version 3, I have to implement the
> new UnivariateDifferentiableFunction interface:
>
> public class MyFunctionNew implements
> UnivariateDifferentiableFunction {
>
> public double value(double x) {
> // example value
> return x*x;
> }
>
> public DerivativeStructure value(DerivativeStructure t) {
>
> // What do I have to do here??
> // return what?
> }
> }
>
> I don't know how to use the DerivativeStructure. What do I have to do,
> to get the same functionality like in the the previous function? How can
> I define the derivative of my function?
> I tried to understand from the user guide, but it wasn't clear for me.
>
> It would be great if someone could give me a hint or further explanation
> on this.
>
> Thank you very much in advance!
>
> Best regards,
> Franz
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [email protected]
> For additional commands, e-mail: [email protected]
>
>
