/// <summary>
/// Convolves the specified finite signal with an infinite signal.
/// </summary>
/// <param name="s1">The finite signal.</param>
/// <param name="s2">The infinite signal.</param>
/// <returns></returns>
/// <exception cref="SamplerateMismatchException"></exception>
public static ISignal Convolve(this IFiniteSignal s1, ISignal s2)
{
if (s1.SampleRate != s2.SampleRate)
{
throw new SamplerateMismatchException();
}
return(new InfiniteSignal(
(start, length) =>
{
var l = s1.Length + Math.Max(s1.Length, length) - 1;
var n = Fft.NextPowerOfTwo(l);
var spectrum1 = Fft.RealFft(s1.Signal, n);
var signal2A = s2.GetWindowedSignal(start - s1.Length - s1.Start, s1.Length);
var spectrum2A = Fft.RealFft(signal2A, n);
var signal2B = s2.GetWindowedSignal(start - s1.Start, length);
var spectrum2B = Fft.RealFft(signal2B, n);
var spectrumA = spectrum1.Multiply(spectrum2A);
var spectrumB = spectrum1.Multiply(spectrum2B);
var signalA = Fft.RealIfft(spectrumA).Skip(s1.Length).Take(Math.Min(length, s1.Length - 1));
var signalB = Fft.RealIfft(spectrumB).Take(length);
var signal = signalA.AddFull(signalB);
return signal;
},
s1.SampleRate)
{
DisplayName = "convolution result"
});
}
protected override Series CreateGraph(ISignal signal)
{
var ret = new ImpulseResponseGraph();
ret.Points.AddRange(
signal.GetWindowedSignal(this.XMin, this.XMax - this.XMin + 1)
.Zip(Enumerable.Range(this.XMin, this.XMax - this.XMin + 1), (m, t) => new DataPoint(t, m)));
return(ret);
//var fsignal = signal as IFiniteSignal;
//if (fsignal != null)
//{
// ret.Points.AddRange(fsignal.Signal.Zip(Enumerable.Range(fsignal.Start, fsignal.Length), (m, t) => new DataPoint(t, m)));
// return ret;
//}
//var esignal = signal as IEnumerableSignal;
//if (esignal != null)
//{
// var wsignal = esignal.Multiply(this.CausalWindow);
// return this.CreateGraph(wsignal);
//}
//var iwsignal = signal.Multiply(this.SymmetricWindow);
//return this.CreateGraph(iwsignal);
}
/// <summary>
/// Negates the specified signal.
/// </summary>
/// <param name="s">The signal.</param>
/// <returns></returns>
public static ISignal Negate(this ISignal s)
{
return(new InfiniteSignal((start, length) => s.GetWindowedSignal(start, length).Negate(), s.SampleRate)
{
DisplayName = "negation result"
});
}
/// <summary>
/// Adds the specified signals.
/// </summary>
/// <param name="s1">The first signal.</param>
/// <param name="s2">The second signal.</param>
/// <returns></returns>
/// <exception cref="SamplerateMismatchException"></exception>
public static ISignal Add(this ISignal s1, ISignal s2)
{
if (s1.SampleRate != s2.SampleRate)
{
throw new SamplerateMismatchException();
}
return(new InfiniteSignal((start, length) => s1.GetWindowedSignal(start, length).Add(s2.GetWindowedSignal(start, length)), s1.SampleRate)
{
DisplayName = "addition result"
});
}
/// <summary>
/// Multiplies the specified finite signal with a signal.
/// </summary>
/// <param name="s1">The finite signal.</param>
/// <param name="s2">The second signal.</param>
/// <returns></returns>
/// <exception cref="SamplerateMismatchException"></exception>
public static IFiniteSignal Multiply(this IFiniteSignal s1, ISignal s2)
{
if (s1.SampleRate != s2.SampleRate)
{
throw new SamplerateMismatchException();
}
return(new FiniteSignal(s1.Signal.Multiply(s2.GetWindowedSignal(s1.Start, s1.Length)).ToReadOnlyList(), s1.SampleRate, s1.Start)
{
DisplayName = "multiplication result"
});
}
/// <summary>
/// Reverses the specified infinite signal.
/// </summary>
/// <param name="signal">The signal.</param>
/// <returns></returns>
public static ISignal Reverse(this ISignal signal)
{
return(new InfiniteSignal((start, length) => signal.GetWindowedSignal(-start - length + 1, length).Reverse(), signal.SampleRate));
}
