private HistogramData GetValleysHistogram(string columnId)
{
var histogram = new HistogramData();
var histogramFields = new Dictionary <double, List <int> >();
double lastValue = 0;
bool increasing = true;
foreach (var field in Data.Fields)
{
if (field.Invalid)
{
continue;
}
double?value = field.GetValue(columnId);
if (!value.HasValue)
{
continue;
}
if (value < lastValue)
{
increasing = false;
}
else if (value > lastValue)
{
if (!increasing)
{
histogram.Add(lastValue);
List <int> fields;
histogramFields.TryGetValue(lastValue, out fields);
if (fields == null)
{
fields = new List <int>();
}
fields.Add(field.FieldNumber);
histogramFields[lastValue] = fields;
}
increasing = true;
}
lastValue = value.Value;
}
return(histogram);
}
private int DetectThreshold(string columnId, out HistogramData histogram)
{
histogram = GetValleysHistogram(columnId);
PrintHistogram(columnId + " Valleys Histogram", histogram);
for (int i = 1; i < 256; i++)
{
int current = histogram[i];
int previous = histogram[i - 1];
if (current < previous)
{
i--;
Log(columnId + " threshold detected: " + i.ToString());
return(i);
}
}
return(0);
}
private void PrintHistogram(string title, HistogramData histogram)
{
Log("");
Log(title);
int firstI = -1;
for (int i = 0; i < 100; i++)
{
int count = histogram[i];
if ((firstI == -1) && (count > 0))
{
firstI = i;
}
if (i > firstI + 20)
{
break;
}
int percentage = 100 * count / histogram.MaximumValue;
Log(i.ToString().PadLeft(3) + ", " + count.ToString().PadLeft(histogram.MaximumValue.ToString().Length) + " : " + "".PadRight(percentage, '*'));
}
}
private HistogramData GetValuesHistogram(string columnId)
{
var histogram = new HistogramData();
foreach (var field in Data.Fields)
{
if (field.Invalid)
{
continue;
}
double?value = field.GetValue(columnId);
if (!value.HasValue)
{
continue;
}
histogram.Add(value.Value);
}
return(histogram);
}