/// <summary>
/// 最小位相を求める。
/// </summary>
/// <returns>変換後</returns>
public double[] GetMinimumPhase()
{
int N = this.x.Length / 2;
double[] tmp = new double[2 * N];
for (int i = 0; i < N; ++i)
{
tmp[2 * i] = Math.Log(this[i].LinearPower);
tmp[2 * i + 1] = 0;
}
CFft fft = new CFft(2 * N);
fft.Invert(tmp);
tmp[0] /= 2; tmp[1] /= 2;
tmp[N] /= 2; tmp[N + 1] /= 2;
for (int i = N + 1; i < 2 * N; ++i)
{
tmp[i] = 0;
}
fft.Transform(tmp);
double[] y = new double[N];
for (int i = 0; i < N; ++i)
{
y[i] = tmp[2 * i + 1] / N;
}
return(y);
} //HilbertTransform
/// <summary>
/// x をヒルベルト変換する。
/// </summary>
/// <param name="x">変換元</param>
/// <returns>変換後</returns>
public static double[] HilbertTransform(double[] x)
{
int N = x.Length;
double[] tmp = new double[2 * N];
for (int i = 0; i < N; ++i)
{
tmp[2 * i] = x[i];
tmp[2 * i + 1] = 0;
}
CFft fft = new CFft(2 * N);
fft.Invert(tmp);
tmp[0] /= 2; tmp[1] /= 2;
tmp[N] /= 2; tmp[N + 1] /= 2;
for (int i = N + 1; i < 2 * N; ++i)
{
tmp[i] = 0;
}
fft.Transform(tmp);
double[] y = new double[x.Length];
for (int i = 0; i < N; ++i)
{
x[i] = tmp[2 * i] * 2 / N;
y[i] = tmp[2 * i + 1] * 2 / N;
}
return(y);
} //HilbertTransform