forked from tsai/mathnet-numerics
diluculo
8 years ago
2 changed files with 399 additions and 0 deletions
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using NUnit.Framework; |
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using System; |
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namespace MathNet.Numerics.UnitTests.SpecialFunctionsTests |
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{ |
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/// <summary>
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/// Kelvin functions tests.
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/// </summary>
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[TestFixture, Category("Functions")] |
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public class KelvinTests |
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{ |
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[Test] |
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public void KelvinBerApprox([Range(-8, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.1
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Assert.AreEqual(Polynomial.Evaluate(x / 8.0, |
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1.0, |
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0.0, 0.0, 0.0, -64.0, 0.0, |
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0.0, 0.0, 113.77777774, 0.0, 0.0, |
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0.0, -32.36345652, 0.0, 0.0, 0.0, |
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2.64191397, 0.0, 0.0, 0.0, -0.08349609, |
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0.0, 0.0, 0.0, 0.00122552, 0.0, |
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0.0, 0.0, -0.00000901), SpecialFunctions.KelvinBer(x), 1e-9); |
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} |
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[Test] |
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public void KelvinBeiApprox([Range(-8, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.2
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Assert.AreEqual(Polynomial.Evaluate(x / 8.0, |
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0.0, |
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0.0, 16.0, 0.0, 0.0, 0.0, |
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-113.77777774, 0.0, 0.0, 0.0, 72.81777742, |
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0.0, 0.0, 0.0, -10.56765779, 0.0, |
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0.0, 0.0, 0.52185615, 0.0, 0.0, |
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0.0, -0.01103667, 0.0, 0.0, 0.0, |
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0.00011346), |
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SpecialFunctions.KelvinBei(x), 6e-9); |
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} |
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[Test] |
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public void KelvinKerApprox([Range(0.25, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.3
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Assert.AreEqual( |
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Polynomial.Evaluate(x / 8.0, |
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-Math.Log(x / 2.0) * SpecialFunctions.KelvinBer(x) + SpecialFunctions.KelvinBei(x) * Constants.PiOver4 - 0.57721566, |
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0.0, 0.0, 0.0, -59.05819744, 0.0, |
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0.0, 0.0, 171.36272133, 0.0, 0.0, |
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0.0, -60.60977451, 0.0, 0.0, 0.0, |
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5.65539121, 0.0, 0.0, 0.0, -0.19636347, |
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0.0, 0.0, 0.0, 0.00309699, 0.0, |
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0.0, 0.0, -0.00002458), |
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SpecialFunctions.KelvinKer(x), 1e-8); |
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} |
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[Test] |
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public void KelvinKeiApprox([Range(0.25, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.4
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Assert.AreEqual( |
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-Math.Log(x / 2.0) * SpecialFunctions.KelvinBei(x) - Constants.PiOver4 * SpecialFunctions.KelvinBer(x) |
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+ Polynomial.Evaluate(x / 8.0, |
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0.0, |
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0.0, 6.76454936, 0.0, 0.0, 0.0, |
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-142.91827687, 0.0, 0.0, 0.0, 124.23569650, |
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0.0, 0.0, 0.0, -21.30060904, 0.0, |
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0.0, 0.0, 1.17509064, 0.0, 0.0, |
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0.0, -0.02695875, 0.0, 0.0, 0.0, |
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0.00029532), |
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SpecialFunctions.KelvinKei(x), 3e-9); |
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} |
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[Test] |
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public void KelvinBerPrimeApprox([Range(-8, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.5
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Assert.AreEqual(x * Polynomial.Evaluate(x / 8.0, |
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0.0, |
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0.0, -4.0, 0.0, 0.0, 0.0, |
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14.22222222, 0.0, 0.0, 0.0, -6.06814810, |
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0.0, 0.0, 0.0, 0.66047849, 0.0, |
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0.0, 0.0, -0.02609253, 0.0, 0.0, |
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0.0, 0.00045957, 0.0, 0.0, 0.0, |
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-0.00000394), SpecialFunctions.KelvinBerPrime(x), 2.1e-8); |
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} |
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[Test] |
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public void KelvinBeiPrimeApprox([Range(-8, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.6
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Assert.AreEqual(x * Polynomial.Evaluate(x / 8.0, |
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0.5, |
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0.0, 0.0, 0.0, -10.66666666, 0.0, |
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0.0, 0.0, 11.37777772, 0.0, 0.0, |
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0.0, -2.31167514, 0.0, 0.0, 0.0, |
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0.14677204, 0.0, 0.0, 0.0, -0.00379386, |
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0.0, 0.0, 0.0, 0.00004609), |
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SpecialFunctions.KelvinBeiPrime(x), 7e-8); |
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} |
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[Test] |
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public void KelvinKerPrimeApprox([Range(0.25, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.7
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Assert.AreEqual( |
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-Math.Log(x / 2.0) * SpecialFunctions.KelvinBerPrime(x) - SpecialFunctions.KelvinBer(x) / x + Constants.PiOver4 * SpecialFunctions.KelvinBeiPrime(x) |
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+ x * Polynomial.Evaluate(x / 8.0, |
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0.0, |
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0.0, -3.69113734, 0.0, 0.0, 0.0, |
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21.42034017, 0.0, 0.0, 0.0, -11.36433272, |
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0.0, 0.0, 0.0, 1.41384780, 0.0, |
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0.0, 0.0, -0.06136358, 0.0, 0.0, |
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0.0, 0.00116137, 0.0, 0.0, 0.0, |
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-0.00001075), |
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SpecialFunctions.KelvinKerPrime(x), 8e-8); |
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} |
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[Test] |
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public void KelvinKeiPrimeApprox([Range(0.25, 8, 0.25)] double x) |
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{ |
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// Approx by Abramowitz/Stegun 9.11.8
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Assert.AreEqual( |
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-Math.Log(x / 2.0) * SpecialFunctions.KelvinBeiPrime(x) - SpecialFunctions.KelvinBei(x) / x - Constants.PiOver4 * SpecialFunctions.KelvinBerPrime(x) |
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+ x * Polynomial.Evaluate(x / 8.0, |
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0.21139217, |
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0.0, 0.0, 0.0, -13.39858846, 0.0, |
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0.0, 0.0, 19.41182758, 0.0, 0.0, |
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0.0, -4.65950823, 0.0, 0.0, 0.0, |
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0.33049424, 0.0, 0.0, 0.0, -0.00926707, |
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0.0, 0.0, 0.0, 0.00011997), |
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SpecialFunctions.KelvinKeiPrime(x), 7e-8); |
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} |
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} |
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} |
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@ -0,0 +1,264 @@ |
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using System; |
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using System.Numerics; |
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namespace MathNet.Numerics |
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{ |
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/// <summary>
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/// This partial implementation of the SpecialFunctions class contains all methods related to the modified Bessel function.
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/// </summary>
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public static partial class SpecialFunctions |
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{ |
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/// <summary>
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/// Returns the Kelvin function of the first kind.
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/// <para>KelvinBe(nu, x) is given by BesselJ(0, j * sqrt(j) * x) where j = sqrt(-1).</para>
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/// <para>KelvinBer(nu, x) and KelvinBei(nu, x) are the real and imaginary parts of the KelvinBe(nu, x)</para>
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/// </summary>
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/// <param name="nu">the order of the the Kelvin function.</param>
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/// <param name="x">The value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function of the first kind.</returns>
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public static Complex KelvinBe(double nu, double x) |
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{ |
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Complex ISqrtI = new Complex(-Constants.Sqrt1Over2, Constants.Sqrt1Over2); // j * sqrt(j) = (-1)^(3/4) = (-1 + j)/sqrt(2)
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return BesselJ(nu, ISqrtI * x); |
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} |
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/// <summary>
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/// Returns the Kelvin function ber.
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/// <para>KelvinBer(nu, x) is given by the real part of BesselJ(nu, j * sqrt(j) * x) where j = sqrt(-1).</para>
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/// </summary>
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/// <param name="nu">the order of the the Kelvin function.</param>
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/// <param name="x">The value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function ber.</returns>
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public static double KelvinBer(double nu, double x) |
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{ |
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return KelvinBe(nu, x).Real; |
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} |
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/// <summary>
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/// Returns the Kelvin function ber.
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/// <para>KelvinBer(x) is given by the real part of BesselJ(0, j * sqrt(j) * x) where j = sqrt(-1).</para>
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/// <para>KelvinBer(x) is equivalent to KelvinBer(0, x).</para>
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/// </summary>
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/// <param name="x">The value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function ber.</returns>
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public static double KelvinBer(double x) |
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{ |
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return KelvinBe(0, x).Real; |
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} |
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/// <summary>
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/// Returns the Kelvin function bei.
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/// <para>KelvinBei(nu, x) is given by the imaginary part of BesselJ(nu, j * sqrt(j) * x) where j = sqrt(-1).</para>
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/// </summary>
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/// <param name="nu">the order of the the Kelvin function.</param>
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/// <param name="x">The value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function bei.</returns>
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public static double KelvinBei(double nu, double x) |
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{ |
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return KelvinBe(nu, x).Imaginary; |
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} |
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/// <summary>
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/// Returns the Kelvin function bei.
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/// <para>KelvinBei(x) is given by the imaginary part of BesselJ(0, j * sqrt(j) * x) where j = sqrt(-1).</para>
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/// <para>KelvinBei(x) is equivalent to KelvinBei(0, x).</para>
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/// </summary>
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/// <param name="x">The value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function bei.</returns>
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public static double KelvinBei(double x) |
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{ |
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return KelvinBe(0, x).Imaginary; |
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} |
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/// <summary>
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/// Returns the derivative of the Kelvin function ber.
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/// </summary>
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/// <param name="nu">The order of the Kelvin function.</param>
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/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
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/// <returns>the derivative of the Kelvin function ber</returns>
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public static double KelvinBerPrime(double nu, double x) |
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{ |
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const double inv2Sqrt2 = 0.35355339059327376220042218105242451964241796884424; // 1/(2 * sqrt(2))
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return inv2Sqrt2 * (-KelvinBer(nu - 1, x) + KelvinBer(nu + 1, x) - KelvinBei(nu - 1, x) + KelvinBei(nu + 1, x)); |
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} |
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/// <summary>
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/// Returns the derivative of the Kelvin function ber.
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/// </summary>
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/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
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/// <returns>The derivative of the Kelvin function ber.</returns>
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public static double KelvinBerPrime(double x) |
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{ |
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return KelvinBerPrime(0, x); |
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} |
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/// <summary>
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/// Returns the derivative of the Kelvin function bei.
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/// </summary>
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/// <param name="nu">The order of the Kelvin function.</param>
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/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
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/// <returns>the derivative of the Kelvin function bei.</returns>
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public static double KelvinBeiPrime(double nu, double x) |
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{ |
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const double inv2Sqrt2 = 0.35355339059327376220042218105242451964241796884424; // 1/(2 * sqrt(2))
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return inv2Sqrt2 * (KelvinBer(nu - 1, x) - KelvinBer(nu + 1, x) - KelvinBei(nu - 1, x) + KelvinBei(nu + 1, x)); |
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} |
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/// <summary>
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/// Returns the derivative of the Kelvin function bei.
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/// </summary>
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/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
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/// <returns>The derivative of the Kelvin function bei.</returns>
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public static double KelvinBeiPrime(double x) |
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{ |
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return KelvinBeiPrime(0, x); |
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} |
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/// <summary>
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/// Returns the Kelvin function of the second kind
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/// <para>KelvinKe(nu, x) is given by Exp(-nu * pi * j / 2) * BesselK(nu, x * sqrt(j)) where j = sqrt(-1).</para>
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/// <para>KelvinKer(nu, x) and KelvinKei(nu, x) are the real and imaginary parts of the KelvinBe(nu, x)</para>
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/// </summary>
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/// <param name="nu">The order of the Kelvin function.</param>
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/// <param name="x">The value to calculate the kelvin function of,</param>
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/// <returns></returns>
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public static Complex KelvinKe(double nu, double x) |
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{ |
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Complex PiIOver2 = new Complex(0.0, Constants.PiOver2); // pi * I / 2
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Complex SqrtI = new Complex(Constants.Sqrt1Over2, Constants.Sqrt1Over2); // sqrt(j) = (-1)^(1/4) = (1 + j)/sqrt(2)
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return Complex.Exp(-nu * PiIOver2) * BesselK(nu, SqrtI * x); |
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} |
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/// <summary>
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/// Returns the Kelvin function ker.
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/// <para>KelvinKer(nu, x) is given by the real part of Exp(-nu * pi * j / 2) * BesselK(nu, sqrt(j) * x) where j = sqrt(-1).</para>
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/// </summary>
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/// <param name="nu">the order of the the Kelvin function.</param>
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/// <param name="x">The non-negative real value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function ker.</returns>
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public static double KelvinKer(double nu, double x) |
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{ |
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if (x <= 0.0) |
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{ |
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throw new ArithmeticException(); |
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} |
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return KelvinKe(nu, x).Real; |
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} |
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/// <summary>
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/// Returns the Kelvin function ker.
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/// <para>KelvinKer(x) is given by the real part of Exp(-nu * pi * j / 2) * BesselK(0, sqrt(j) * x) where j = sqrt(-1).</para>
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/// <para>KelvinKer(x) is equivalent to KelvinKer(0, x).</para>
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/// </summary>
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/// <param name="x">The non-negative real value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function ker.</returns>
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public static double KelvinKer(double x) |
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{ |
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if (x <= 0.0) |
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{ |
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throw new ArithmeticException(); |
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} |
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return KelvinKe(0, x).Real; |
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} |
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/// <summary>
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/// Returns the Kelvin function kei.
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/// <para>KelvinKei(nu, x) is given by the imaginary part of Exp(-nu * pi * j / 2) * BesselK(nu, sqrt(j) * x) where j = sqrt(-1).</para>
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/// </summary>
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/// <param name="nu">the order of the the Kelvin function.</param>
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/// <param name="x">The non-negative real value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function kei.</returns>
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public static double KelvinKei(double nu, double x) |
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{ |
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if (x <= 0.0) |
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{ |
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throw new ArithmeticException(); |
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} |
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return KelvinKe(nu, x).Imaginary; |
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} |
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/// <summary>
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/// Returns the Kelvin function kei.
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/// <para>KelvinKei(x) is given by the imaginary part of Exp(-nu * pi * j / 2) * BesselK(0, sqrt(j) * x) where j = sqrt(-1).</para>
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/// <para>KelvinKei(x) is equivalent to KelvinKei(0, x).</para>
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/// </summary>
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/// <param name="x">The non-negative real value to compute the Kelvin function of.</param>
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/// <returns>The Kelvin function kei.</returns>
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public static double KelvinKei(double x) |
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{ |
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if (x <= 0.0) |
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{ |
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throw new ArithmeticException(); |
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} |
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return KelvinKe(0, x).Imaginary; |
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} |
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/// <summary>
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/// Returns the derivative of the Kelvin function ker.
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/// </summary>
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/// <param name="nu">The order of the Kelvin function.</param>
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/// <param name="x">The non-negative real value to compute the derivative of the Kelvin function of.</param>
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/// <returns>The derivative of the Kelvin function ker.</returns>
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public static double KelvinKerPrime(double nu, double x) |
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{ |
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if (x <= 0.0) |
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{ |
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throw new ArithmeticException(); |
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} |
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const double inv2Sqrt2 = 0.35355339059327376220042218105242451964241796884424; // 1/(2 * sqrt(2))
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return inv2Sqrt2 * (-KelvinKer(nu - 1, x) + KelvinKer(nu + 1, x) - KelvinKei(nu - 1, x) + KelvinKei(nu + 1, x)); |
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} |
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|
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/// <summary>
|
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|
/// Returns the derivative of the Kelvin function ker.
|
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|
/// </summary>
|
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|
/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
|
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|
/// <returns>The derivative of the Kelvin function ker.</returns>
|
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|
public static double KelvinKerPrime(double x) |
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|
{ |
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|
if (x <= 0.0) |
||||
|
{ |
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|
throw new ArithmeticException(); |
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|
} |
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|
|
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|
return KelvinKerPrime(0, x); |
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|
} |
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|
|
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|
/// <summary>
|
||||
|
/// Returns the derivative of the Kelvin function kei.
|
||||
|
/// </summary>
|
||||
|
/// <param name="nu">The order of the Kelvin function.</param>
|
||||
|
/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
|
||||
|
/// <returns>The derivative of the Kelvin function kei.</returns>
|
||||
|
public static double KelvinKeiPrime(double nu, double x) |
||||
|
{ |
||||
|
if (x <= 0.0) |
||||
|
{ |
||||
|
throw new ArithmeticException(); |
||||
|
} |
||||
|
|
||||
|
const double inv2Sqrt2 = 0.35355339059327376220042218105242451964241796884424; // 1/(2 * sqrt(2))
|
||||
|
return inv2Sqrt2 * (KelvinKer(nu - 1, x) - KelvinKer(nu + 1, x) - KelvinKei(nu - 1, x) + KelvinKei(nu + 1, x)); |
||||
|
} |
||||
|
|
||||
|
/// <summary>
|
||||
|
/// Returns the derivative of the Kelvin function kei.
|
||||
|
/// </summary>
|
||||
|
/// <param name="x">The value to compute the derivative of the Kelvin function of.</param>
|
||||
|
/// <returns>The derivative of the Kelvin function kei.</returns>
|
||||
|
public static double KelvinKeiPrime(double x) |
||||
|
{ |
||||
|
if (x <= 0.0) |
||||
|
{ |
||||
|
throw new ArithmeticException(); |
||||
|
} |
||||
|
|
||||
|
return KelvinKeiPrime(0, x); |
||||
|
} |
||||
|
} |
||||
|
} |
||||
Loading…
Reference in new issue