/// <summary>
/// Analyzes an array of events or hits, represented by a binary of matrix.
/// Assumes a Poisson distribution
/// Returns an array of Z-scores indicating the probability at any time or frame that the number of hits occuring
/// in the window centered on that point could have occured by chance.
/// </summary>
public static void AnalyzeClustersOfHits(int[] hits, int window, double thresholdZ, int thresholdCount,
out double[] zScores, out double expectedHits, out double sd)
{
int frameCount = hits.Length;
int hitCount = DataTools.CountPositives(hits);
expectedHits = (double)hitCount * window / frameCount;
// assume Poisson Distribution
sd = Math.Sqrt(expectedHits);
// LoggedConsole.WriteLine("hitCount="+hitCount+" expectedHits = " + expectedHits + "+/-" + sd+" thresholdSum="+thresholdSum);
int offset = (int)(window * 0.5); // assign score to position in window
int sum = 0;
for (int i = 0; i < window; i++)
{
// set up the song window
if (hits[i] > 0)
{
sum++;
}
}
// now calculate z-scores for the number of syllable hits in a window
zScores = new double[frameCount];
for (int i = window; i < frameCount; i++)
{
if (sum < thresholdCount)
{
// not enough hits to constitute a cluster - set ascore to neg value
zScores[i - offset] = -10.0;
}
else
{
zScores[i - offset] = (sum - expectedHits) / sd;
}
sum = sum - hits[i - window] + hits[i]; // move the songwindow
}
}