//******************************************************************************************************//  WaveFit.cs - Gbtc////  Copyright © 2012, Grid Protection Alliance.  All Rights Reserved.////  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See//  the NOTICE file distributed with this work for additional information regarding copyright ownership.//  The GPA licenses this file to you under the MIT License (MIT), 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.opensource.org/licenses/MIT////  Unless agreed to in writing, the subject software distributed under the License is distributed on an//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the//  License for the specific language governing permissions and limitations.////  Code Modification History://  ----------------------------------------------------------------------------------------------------//  06/19/2012 - Stephen C. Wills//       Generated original version of source code.//  12/14/2012 - Starlynn Danyelle Gilliam//       Modified Header.////****************************************************************************************************** using System; namespace GSF.NumericalAnalysis{    /// <summary>    /// Represents a sine wave of the form <c>y=A*sin(ω*t+Φ)+δ</c>.    /// </summary>    public struct SineWave    {        /// <summary>        /// 2 * pi        /// </summary>        public const double TwoPi = 2.0 * Math.PI;         /// <summary>        /// Amplitude (A) of the sine wave.        /// </summary>        public double Amplitude;         /// <summary>        /// Frequency (ω) of the sine wave, in Hz.        /// </summary>        public double Frequency;         /// <summary>        /// Phase (Φ) shift of the sine wave.        /// </summary>        public double Phase;         /// <summary>        /// Vertical offset (δ) of the sine wave.        /// </summary>        public double Bias;         /// <summary>        /// Calculates the y-value for the given time.        /// </summary>        /// <param name="t">The time, in seconds.</param>        /// <returns><c>A*sin(ω*t+Φ)+δ</c></returns>        public double CalculateY(double t)        {            return Amplitude * Math.Sin(TwoPi * Frequency * t + Phase) + Bias;        }    }     /// <summary>    /// Linear regression algorithm for sine waves.    /// </summary>    public static class WaveFit    {        /// <summary>        /// Uses least squares linear regression to calculate the best fit sine wave for the given data.        /// </summary>        /// <param name="yValues">The y values of the data points.</param>        /// <param name="tValues">The time values of the data points, in seconds.</param>        /// <param name="frequency">The frequency of the sine wave, in Hz.</param>        /// <returns>A <see cref="SineWave"/> approximated from the given data points.</returns>        public static SineWave SineFit(double[] yValues, double[] tValues, double frequency)        {            double[] z = yValues;            double[] x = new double[tValues.Length];            double[] y = new double[tValues.Length];            double a, b, d;             double rad = 2.0D * Math.PI * frequency;             for (int i = 0; i < tValues.Length; i++)            {                double angle = rad * tValues[i];                x[i] = Math.Sin(angle);                y[i] = Math.Cos(angle);            }             CurveFit.LeastSquares(z, x, y, out d, out a, out b);             return new SineWave            {                Amplitude = Math.Sqrt(a * a + b * b),                Frequency = frequency,                Phase = Math.Atan2(b, a),                Bias = d            };        }    }}