org.apache.commons.math3.transform.DftNormalization Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of commons-math3 Show documentation
Show all versions of commons-math3 Show documentation
The Apache Commons Math project is a library of lightweight, self-contained mathematics and statistics components addressing the most common practical problems not immediately available in the Java programming language or commons-lang.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.transform;
/**
* This enumeration defines the various types of normalizations that can be
* applied to discrete Fourier transforms (DFT). The exact definition of these
* normalizations is detailed below.
*
* @see FastFourierTransformer
* @since 3.0
*/
public enum DftNormalization {
/**
* Should be passed to the constructor of {@link FastFourierTransformer}
* to use the standard normalization convention. This normalization
* convention is defined as follows
*
* - forward transform: yn = ∑k=0N-1
* xk exp(-2πi n k / N),
* - inverse transform: xk = N-1
* ∑n=0N-1 yn exp(2πi n k / N),
*
* where N is the size of the data sample.
*/
STANDARD,
/**
* Should be passed to the constructor of {@link FastFourierTransformer}
* to use the unitary normalization convention. This normalization
* convention is defined as follows
*
* - forward transform: yn = (1 / √N)
* ∑k=0N-1 xk
* exp(-2πi n k / N),
* - inverse transform: xk = (1 / √N)
* ∑n=0N-1 yn exp(2πi n k / N),
*
* which makes the transform unitary. N is the size of the data sample.
*/
UNITARY;
}