/// <summary>
/// Correlates the master and slave timeseries
/// </summary>
/// <returns>A tuple containing the lag , correlation and any error messages</returns>
public (long[], float[], string errorMessage) CorrelateSignals(Type pageType)
{
string errorMessage = null;
Timeserie masterTimerserie = new Timeserie();
Timeserie slaveTimerserie = new Timeserie();
for (int i = _masterTimerserie.Count - 1; i > -1; i--)
{
if (_masterTimerserie[i] is TableColumn)
{
masterTimerserie.AddData(_masterTimerserie[i]);
if (pageType.Name == "HeadToHead")
{
break;
}
}
}
for (int i = _slaveTimerserie.Count - 1; i > -1; i--)
{
if (_slaveTimerserie[i] is TableColumn)
{
slaveTimerserie.AddData(_slaveTimerserie[i]);
if (pageType.Name == "HeadToHead")
{
break;
}
}
}
if ((masterTimerserie.Count) != (slaveTimerserie.Count))
{
errorMessage = "There must be equally many signals in the slave and master timeseries.";
return(null, null, errorMessage);
}
if (masterTimerserie.Count == 0)
{
errorMessage = "The master timeseries must at least consist of one signal";
return(null, null, errorMessage);
}
ResampleTimeserie(masterTimerserie, slaveTimerserie);
masterTimerserie.RemoveBias();
slaveTimerserie.RemoveBias();
masterTimerserie.ToHilbertEnvelope();
slaveTimerserie.ToHilbertEnvelope();
AdjustLengthOfTimeserie(masterTimerserie, slaveTimerserie);
var cor = CrossCorrelation(masterTimerserie.DataAsSignleArray, slaveTimerserie.DataAsSignleArray);
int zeroIndex = (int)Math.Ceiling(((masterTimerserie.Length * masterTimerserie.Count * 2f) - 1) / 2);
int fromIndex = zeroIndex - masterTimerserie.Length + slaveTimerserie.NrZeros;
int nrInterestingSamples = (masterTimerserie.Length + slaveTimerserie.Length - slaveTimerserie.NrZeros - masterTimerserie.NrZeros) - 1;
cor = cor.Skip(fromIndex).Take(nrInterestingSamples).ToArray();
var timelag = IndexToTime(masterTimerserie, slaveTimerserie, cor.Length);
return(timelag, cor, errorMessage);
}
/// <summary>
/// If the master timeseries have a longer duration compared to the slave timeseries and we use multiple signals to
/// sync the timeseries, we need to zero pad the slaves.
/// </summary>
/// <param name="masterTimerseries"></param>
/// <param name="slaveTimerseries"></param>
private void AdjustLengthOfTimeserie(Timeserie masterTimerserie, Timeserie slaveTimerserie)
{
if (masterTimerserie.Length > slaveTimerserie.Length)
{
int nrZeros = masterTimerserie.Length - slaveTimerserie.Length;
slaveTimerserie.ZeroPad(nrZeros);
}
if (slaveTimerserie.Length > masterTimerserie.Length)
{
int nrZeros = slaveTimerserie.Length - masterTimerserie.Length;
masterTimerserie.ZeroPad(nrZeros);
}
}
/// <summary>
/// Resamples the timeseries. The timeserie of the lowest sampling frequency is resampled to
/// the same sampling frequency as the other timeserie
/// </summary>
/// <param name="masterTimerseries"></param>
/// <param name="slaveTimerseries"></param>
private void ResampleTimeserie(Timeserie masterTimerserie, Timeserie slaveTimerserie)
{
if (masterTimerserie.SamplingFreq == slaveTimerserie.SamplingFreq)
{
return;
}
else if (masterTimerserie.SamplingFreq > slaveTimerserie.SamplingFreq)
{
slaveTimerserie.Resample(masterTimerserie.SamplingFreq);
}
else
{
masterTimerserie.Resample(slaveTimerserie.SamplingFreq);
}
}
/// <summary>
/// maps the index nr to a time lag
/// </summary>
/// <param name="master"></param>
/// <param name="slave"></param>
/// <param name="nrSamples"></param>
/// <returns> A array mapping index to a time lag </returns>
private long[] IndexToTime(Timeserie master, Timeserie slave, int nrSamples)
{
long durationSlave = slave.Time.Data[slave.Length - 1 - slave.NrZeros] - slave.Time.Data[0];
long durationMaster = master.Time.Data[master.Length - 1 - master.NrZeros] - master.Time.Data[0];
long shiftedFromZero = slave.Time.Data[0] - master.Time.Data[0];
long startTime = shiftedFromZero + durationSlave;
long endTime = startTime - durationMaster - durationSlave;
long duration = Math.Abs(startTime - endTime);
float sampleTime = duration / (nrSamples - 1);
long[] timeShift = new long[nrSamples];
for (int i = 0; i < nrSamples; i++)
{
timeShift[i] = (long)-(startTime - (i * sampleTime));
}
return(timeShift);
}
