double ArduinoComparer::computeError(
const Trajectory &aT
, const Trajectory &dT
, double offsetSeconds
) const
{
double sum = 0;
// Check each reading in the device trajectory. Find its time and
// shift it. Then read the value from the Arduino trace at the
// shifted time and run its value through the mapping to find the
// expected device value at that time. Compute the sum of squared
// errors.
// Because we want a positive offset to correspond to the device
// measurements being behind the Arduino, we need to offset the
// Arduino measurements by the negative of the offset.
for (size_t i = 0; i < dT.m_entries.size(); i++) {
double deviceValue = dT.m_entries[i].m_value;
double timeShifted = dT.m_entries[i].m_time - offsetSeconds;
size_t arduinoValue = static_cast<size_t>(aT.lookup(timeShifted));
double expectedDeviceValue = m_mappingMean[arduinoValue];
sum += (expectedDeviceValue - deviceValue) *
(expectedDeviceValue - deviceValue);
}
return sum;
}
