/*
 * 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.math.transform;

import org.apache.commons.math.FunctionEvaluationException;
import org.apache.commons.math.analysis.UnivariateRealFunction;
import org.apache.commons.math.complex.Complex;

/**
 * Interface for one-dimensional data sets transformations producing real
 * results.
 * <p>
 * Such transforms include {@link FastSineTransformer sine transform},
 * {@link FastCosineTransformer cosine transform} or
 * {@link FastHadamardTransformer Hadamard transform}.
 * {@link FastFourierTransformer Fourier transform} is of a different kind and
 * does not implement this interface since it produces {@link Complex complex}
 * results instead of real ones.
 * </p>
 * 
 * @version $Revision$ $Date$
 * @since 2.0
 */
public interface RealTransformer {

	/**
	 * Transform the given real data set.
	 * 
	 * @param f
	 *            the real data array to be transformed (signal)
	 * @return the real transformed array (spectrum)
	 * @throws IllegalArgumentException
	 *             if any parameters are invalid
	 */
	double[] transform(double f[]) throws IllegalArgumentException;

	/**
	 * Transform the given real function, sampled on the given interval.
	 * 
	 * @param f
	 *            the function to be sampled and transformed
	 * @param min
	 *            the lower bound for the interval
	 * @param max
	 *            the upper bound for the interval
	 * @param n
	 *            the number of sample points
	 * @return the real transformed array
	 * @throws FunctionEvaluationException
	 *             if function cannot be evaluated at some point
	 * @throws IllegalArgumentException
	 *             if any parameters are invalid
	 */
	double[] transform(UnivariateRealFunction f, double min, double max, int n)
			throws FunctionEvaluationException, IllegalArgumentException;

	/**
	 * Inversely transform the given real data set.
	 * 
	 * @param f
	 *            the real data array to be inversely transformed (spectrum)
	 * @return the real inversely transformed array (signal)
	 * @throws IllegalArgumentException
	 *             if any parameters are invalid
	 */
	public abstract double[] inversetransform(double f[]) throws IllegalArgumentException;

	/**
	 * Inversely transform the given real function, sampled on the given
	 * interval.
	 * 
	 * @param f
	 *            the function to be sampled and inversely transformed
	 * @param min
	 *            the lower bound for the interval
	 * @param max
	 *            the upper bound for the interval
	 * @param n
	 *            the number of sample points
	 * @return the real inversely transformed array
	 * @throws FunctionEvaluationException
	 *             if function cannot be evaluated at some point
	 * @throws IllegalArgumentException
	 *             if any parameters are invalid
	 */
	double[] inversetransform(UnivariateRealFunction f, double min, double max, int n)
			throws FunctionEvaluationException, IllegalArgumentException;

}