private static IEnumerable <TimeInterval> GetStressfulSpansForHealthIndicator(
IEnumerable <StateRecord> statesOfPerson,
Func <StateRecord, float> healthIndicatorExtractor,
IndicatorParameters parameters)
{
DateTime begin = statesOfPerson.First().CreateTime;
var normalizedStates = statesOfPerson.Select(state => new PhysicalState
{
StateIndicator = healthIndicatorExtractor(state),
Time = state.CreateTime
}).ToArray();
double mean = normalizedStates.Select(state => state.StateIndicator).Average();
double stdev = StandardDeviation(normalizedStates.Select(state => state.StateIndicator));
int abnormalValuesInRow = 0;
for (int i = 0; i < normalizedStates.Length; i++)
{
PhysicalState state = normalizedStates[i];
float indicator = state.StateIndicator;
bool isAbnormalValue = indicator - mean >= parameters.SigmaCoefficient * stdev;
bool isLastRecord = i == normalizedStates.Length - 1;
if (isAbnormalValue && !isLastRecord)
{
abnormalValuesInRow++;
}
else if (abnormalValuesInRow > 0)
{
var interval = new TimeInterval
{
Begin = normalizedStates[i - abnormalValuesInRow - 1].Time,
End = normalizedStates[i].Time
};
if (interval.GetDurationInSeconds() >= parameters.MinDurationSeconds)
{
yield return(interval);
}
abnormalValuesInRow = 0;
}
}
}
