code.txt

int findNextSampleWithinRange(float *data1, float *data2,
	int current_index, int last_index,
	float thresholdLo1, float thresholdHi1,
	float thresholdLo2, float thresholdHi2)
{
	if (data2)
	{
		// loop while the current sample of either data1 or data2 is outside the range of interest
		while (current_index <= last_index &&
			((data1[current_index] <= thresholdLo1 || data1[current_index] >= thresholdHi1) ||
			 (data2[current_index] <= thresholdLo2 || data2[current_index] >= thresholdHi2)))
		{
			current_index++;
		}
	}
	else
	{
		// loop while the current sample is outside the range of interest
		while (current_index <= last_index &&
			(data1[current_index] <= thresholdLo1 || data1[current_index] >= thresholdHi1))
		{
			current_index++;
		}
	}

	return current_index;
}

int findNextSampleOutsideRange(float *data1, float *data2,
	int current_index, int last_index,
	float thresholdLo1, float thresholdHi1,
	float thresholdLo2, float thresholdHi2)
{
	if (data2)
	{
		// loop while the current sample of either data1 and data2 is within the range of interest
		while (current_index <= last_index &&
			data1[current_index] > thresholdLo1 && data1[current_index] < thresholdHi1 &&
			data2[current_index] > thresholdLo2 && data2[current_index] < thresholdHi2)
		{
			current_index++;
		}
	}
	else
	{
		// loop while the current sample is within the range of interest
		while (current_index <= last_index &&
			data1[current_index] > thresholdLo1 && data1[current_index] < thresholdHi1)
		{
			current_index++;
		}
	}

	return current_index;
}

std::vector<std::pair<int,int>> performContinuitySearch(float *data1, float *data2,
	int indexBegin, int indexEnd,
	float thresholdLo1, float thresholdHi1,
	float thresholdLo2, float thresholdHi2,
	int winLength)
{
	// we would probably do some input validation here in production code!

	std::vector<std::pair<int, int>> vecContinuities;

	// loop from indexBegin to indexEnd-winLength
	// if we get within winLength samples from indexEnd, we no longer need to search
	int i = indexBegin;
	while (i <= indexEnd-winLength)
	{
		i = findNextSampleWithinRange(data1, data2, i, indexEnd-winLength,
			thresholdLo1, thresholdHi1, thresholdLo2, thresholdHi2);

		// store the index of the first sample within the range of interest
		int start_index = i;
		i = findNextSampleOutsideRange(data1, data2, i, indexEnd,
			thresholdLo1, thresholdHi1, thresholdLo2, thresholdHi2);

		// compute the number of consecutive samples within the range of interest
		int length_of_continuity = i-start_index+1;

		// if the continuity is long enough, then add it to our collection
		if (length_of_continuity >= winLength) {
			// Success: We can return the start index and the current index since we have
			// counted the required number of samples
			vecContinuities.push_back(std::make_pair(start_index, i-1));
		}
	}

	// return any continuities that have been found
	return vecContinuities;
}

int searchContinuityAboveValue(float *data, int indexBegin, int indexEnd, float threshold, int winLength)
{
	std::vector<std::pair<int,int>> vecContinuities =
		performContinuitySearch(data, NULL, indexBegin, indexEnd,
		threshold, std::numeric_limits<double>::infinity(),
		0.0, 0.0, winLength);

	if (vecContinuities.empty())
		return -1;

	std::pair<int,int> pair = vecContinuities[0];
	return pair.first;
}

int backSearchContinuityWithinRange(float *data, int indexBegin, int indexEnd, float thresholdLo, float thresholdHi, int winLength)
{
	// swapped indexBegin and indexEnd indices because search is backward (indexBegin > indexEnd)
	std::vector<std::pair<int,int>> vecContinuities =
		performContinuitySearch(data, NULL, indexEnd, indexBegin,
		thresholdLo, thresholdHi,
		0.0, 0.0, winLength);

	if (vecContinuities.empty())
		return -1;

	// return second index of last continuity pair
	std::pair<int,int> pair = vecContinuities.back();
	return pair.second;
}

int searchContinuityAboveValueTwoSignals(float *data1, float *data2, int indexBegin, int indexEnd, float threshold1, float threshold2, int winLength)
{
	std::vector<std::pair<int,int>> vecContinuities =
		performContinuitySearch(data1, data2, indexBegin, indexEnd,
		threshold1, std::numeric_limits<double>::infinity(),
		threshold2, std::numeric_limits<double>::infinity(), winLength);

	if (vecContinuities.empty())
		return -1;

	std::pair<int,int> pair = vecContinuities[0];
	return pair.first;
}

std::vector<std::pair<int, int>> searchMultiContinuityWithinRange(float *data,
	int indexBegin, int indexEnd, float thresholdLo, float thresholdHi, int winLength)
{
	return performContinuitySearch(data, NULL, indexBegin, indexEnd,
		thresholdLo, thresholdHi, 0.0, 0.0, winLength);
}

// being that this code is being written in C, we could use a simple 
// data structure such as the following to store our swing data:
struct SwingData {
	int *timeStamp;
	float *Ax;
	float *Ay;
	float *Az;
	float *Wx;
	float *Wy;
	float *Wz;
};

// Then the functions above could be called as follows:
int indexBegin = 100;
int indexEnd = 1000;
float threshold = 10.0;
int winLength = 3;
int first_index = searchContinuityAboveValue(swing_data.Ax, indexBegin, indexEnd, threshold, winLength);
if (first_index == -1)
{
	// Failed to find 'winLength' conectutive samples above the threshold!
}
else
{
	// success!
}