org.apache.commons.math3.transform

Class FastHadamardTransformer

java.lang.Object

org.apache.commons.math3.transform.FastHadamardTransformer

All Implemented Interfaces:

Serializable, RealTransformer

public class FastHadamardTransformer
extends Object
implements RealTransformer, Serializable

Implements the Fast Hadamard Transform (FHT). Transformation of an input vector x to the output vector y.

In addition to transformation of real vectors, the Hadamard transform can transform integer vectors into integer vectors. However, this integer transform cannot be inverted directly. Due to a scaling factor it may lead to rational results. As an example, the inverse transform of integer vector (0, 1, 0, 1) is rational vector (1/2, -1/2, 0, 0).

Since:

2.0

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
FastHadamardTransformer()

Method Summary

Modifier and Type	Method and Description
double[]	transform(double[] f, TransformType type) Returns the (forward, inverse) transform of the specified real data set.
int[]	transform(int[] f) Returns the forward transform of the specified integer data set.The integer transform cannot be inverted directly, due to a scaling factor which may lead to double results.
double[]	transform(UnivariateFunction f, double min, double max, int n, TransformType type) Returns the (forward, inverse) transform of the specified real function, sampled on the specified interval.

Methods inherited from class java.lang.Object

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

Constructor Detail

FastHadamardTransformer

public FastHadamardTransformer()

Method Detail

transform

public double[] transform(double[] f,
                          TransformType type)

Returns the (forward, inverse) transform of the specified real data set.

Specified by:

transform in interface RealTransformer

Parameters:

f - the real data array to be transformed (signal)

type - the type of transform (forward, inverse) to be performed

Returns:

the real transformed array (spectrum)

Throws:

MathIllegalArgumentException - if the length of the data array is not a power of two

transform

public double[] transform(UnivariateFunction f,
                          double min,
                          double max,
                          int n,
                          TransformType type)

Returns the (forward, inverse) transform of the specified real function, sampled on the specified interval.

Specified by:

transform in interface RealTransformer

Parameters:

f - the function to be sampled and transformed

min - the (inclusive) lower bound for the interval

max - the (exclusive) upper bound for the interval

n - the number of sample points

type - the type of transform (forward, inverse) to be performed

Returns:

the real transformed array

Throws:

NonMonotonicSequenceException - if the lower bound is greater than, or equal to the upper bound

NotStrictlyPositiveException - if the number of sample points is negative

MathIllegalArgumentException - if the number of sample points is not a power of two

transform

public int[] transform(int[] f)

Returns the forward transform of the specified integer data set.The integer transform cannot be inverted directly, due to a scaling factor which may lead to double results.

Parameters:

f - the integer data array to be transformed (signal)

Returns:

the integer transformed array (spectrum)

Throws:

MathIllegalArgumentException - if the length of the data array is not a power of two