/// <summary>
/// Sets the false discovery rate by creating a histogram of the mass errors and comparing the proportion above a threshhold to the area below.
/// </summary>
private void SetMassErrorHistogramFdr()
{
// Populate the mass error list and create the histogram.
var massErrorList = MatchList.Select(match => match.DifferenceVector[1, 1]).ToList();
var histogramList = MathUtilities.GetHistogramValues(massErrorList, m_matchParameters.HistogramBinWidth);
var peakIndex = 0;
var peakValue = 0.0;
var upperBound = 0.0;
var lowerBound = 0.0;
var meanValue = 0.0;
// Find the maximum and average values.
for (var i = 0; i < histogramList.Count; i++)
{
var bin = histogramList[i];
if (bin.Y > peakValue)
{
peakValue = bin.Y;
peakIndex = i;
}
meanValue += bin.Y;
}
meanValue /= histogramList.Count;
// Set the threshold to a value between the peak and the average value.
var threshold = meanValue + m_matchParameters.HistogramMultiplier * (peakValue - meanValue);
// Find the upper bound.
for (var i = peakIndex; i < histogramList.Count; i++)
{
var bin = histogramList[i];
var lowerBin = histogramList[i - 1];
if (bin.Y < threshold && lowerBin.Y >= threshold)
{
upperBound = lowerBin.X + (lowerBin.Y - threshold) / (lowerBin.Y - bin.Y) * (bin.X - lowerBin.X);
}
}
// Find the lower bound.
for (var i = peakIndex; i >= 0; i--)
{
var bin = histogramList[i];
var upperBin = histogramList[i + 1];
if (bin.Y < threshold && upperBin.Y >= threshold)
{
lowerBound = bin.X + (threshold - bin.Y) / (upperBin.Y - bin.Y) * (upperBin.X - bin.X);
}
}
// Count the number of matches within the bounds and calculate the FDR.
var countInBounds = massErrorList.Count(massDifference => massDifference >= lowerBound && massDifference <= upperBound);
ErrorHistogramFdr = countInBounds / ((upperBound - lowerBound) * threshold);
}