# Class Dfdx

All Implemented Interfaces:
Function<Vector,Double>, RealScalarFunction, UnivariateRealFunction

public class Dfdx
The first derivative is a measure of how a function changes as its input changes. In other words, a derivative is how much a quantity changes if the input changes (by a very small amount). The derivative of a function at a particular point is the best linear approximation of the function at that point. For a univariate real function, the derivative at a point is the slope of the tangent line to the function at that point.

This implementation is a simple wrapper class around the built-in derivative functions, e.g., DBeta, DErf, and the numerical derivative computation classes, e.g., FiniteDifference and Ridders.

• ## Nested Class Summary

Nested Classes
Modifier and Type
Class
Description
static enum
Dfdx.Method
the available methods to compute the numerical derivative

## Nested classes/interfaces inherited from interface dev.nm.analysis.function.Function

Function.EvaluationException
• ## Constructor Summary

Constructors
Constructor
Description
Dfdx(UnivariateRealFunction f)
Construct, using the central finite difference, the first order derivative function of a univariate function f.
Dfdx(UnivariateRealFunction f, Dfdx.Method method)
Construct the first order derivative function of a univariate function f.
• ## Method Summary

Modifier and Type
Method
Description
double
evaluate(double x)
Evaluate y = f(x).

### Methods inherited from class dev.nm.analysis.function.rn2r1.univariate.AbstractUnivariateRealFunction

evaluate

### Methods inherited from class dev.nm.analysis.function.rn2r1.AbstractRealScalarFunction

dimensionOfDomain, dimensionOfRange

### Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

### Methods inherited from interface dev.nm.analysis.function.Function

dimensionOfDomain, dimensionOfRange
• ## Constructor Details

• ### Dfdx

public Dfdx(UnivariateRealFunction f, Dfdx.Method method)
Construct the first order derivative function of a univariate function f.
Parameters:
f - a univariate function
method - the numerical method to use, c.f., Dfdx.Method
• ### Dfdx

public Dfdx
Construct, using the central finite difference, the first order derivative function of a univariate function f.
Parameters:
f - a univariate function
• ## Method Details

• ### evaluate

public double evaluate(double x)
Description copied from interface: UnivariateRealFunction
Evaluate y = f(x).
Parameters:
x - x
Returns:
f(x)