Stats.cpp

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#include "MovingAverage.h"
#include "UnitTestFramework.h"
 
namespace cmlabs {
 
Stats::Stats(uint32 maxCount) {
    this->maxCount = maxCount;
}
 
Stats::~Stats() {
    mutex.enter();
    entries.clear();
    mutex.leave();
}
 
bool Stats::clear() {
    mutex.enter();
    entries.clear();
    mutex.leave();
    return true;
}
 
bool Stats::add(double val) {
    mutex.enter();
    entries.push_back(val);
    while (entries.size() > maxCount)
        entries.pop_front();
    mutex.leave();
    return true;
}
 
double Stats::getSum() {
    double result = 0;
    mutex.enter();
    std::list<double>::iterator i, e;
    for (i=entries.begin(), e=entries.end(); i!=e; i++)
        result += *i;
    mutex.leave();
    return result;
}
 
double Stats::getAverage() {
    double result;
    mutex.enter();
    result = getSum()/entries.size();
    mutex.leave();
    return result;
}
 
double Stats::getVariance() {
    double variance, average, size;
    mutex.enter();
    if ( (size = (double)entries.size()) <= 1) {
        mutex.leave();
        return 0;
    }
    variance = 0;
    average = getSum()/size;
    std::list<double>::iterator i, e;
    for (i=entries.begin(), e=entries.end(); i!=e; i++)
        variance += (*i-average)*(*i-average);
    variance /= size;
    mutex.leave();
    return variance;
}
 
double Stats::getMedian() {
    double result;
    uint32 size, half;
    mutex.enter();
    size = (uint32)entries.size();
    if (!size) { mutex.leave(); return 0; }
    else if (size == 1) { result = entries.front(); mutex.leave(); return result; }
    else if (size == 2) { result = (entries.front() + entries.back()) / 2.0; mutex.leave(); return result; }
 
    half = size / 2;
    entries.sort();
    std::list<double>::iterator i = entries.begin(), e = entries.end();
    if (size % 2) {
        // odd count: the middle element is at index half
        for (uint32 n = 0; n < half; n++)
            i++;
        result = *i;
    }
    else {
        // even count: average the two middle elements at indices half-1 and half
        for (uint32 n = 0; n < half - 1; n++)
            i++;
        result = *i;
        i++;
        result = (result + (*i)) / 2.0;
    }
    mutex.leave();
    return result;
}
 
double Stats::getStdDev() {
    return sqrt(getVariance());
}
 
uint32 Stats::getCount() {
    uint32 result;
    mutex.enter();
    result = (uint32)entries.size();
    mutex.leave();
    return result;
}
 
 
bool Stats::UnitTest() {
    unittest::progress(10, "populate sample");
    Stats stats;
    stats.add(1);
    stats.add(3);
    stats.add(10);
    stats.add(-5);
    stats.add(8);
    stats.add(100);
    stats.add(10);
    stats.add(1);
 
    unittest::progress(30, "count and sum");
    if (stats.getCount() != 8) {
        unittest::fail("Stats test: getCount expected 8, got %u", stats.getCount());
        return false;
    }
    if (stats.getSum() != 128) {
        unittest::fail("Stats test: getSum expected 128, got %f", stats.getSum());
        return false;
    }
 
    unittest::progress(50, "average");
    if (stats.getAverage() != 16) {
        unittest::fail("Stats test: getAverage expected 16, got %f", stats.getAverage());
        return false;
    }
 
    unittest::progress(65, "median");
    // Sorted sample: {-5, 1, 1, 3, 8, 10, 10, 100}; even count -> mean of the two
    // middle elements (3 and 8) -> 5.5
    if (stats.getMedian() != 5.5) {
        unittest::fail("Stats test: getMedian expected 5.5, got %f", stats.getMedian());
        return false;
    }
 
    unittest::progress(80, "variance");
    // Population variance (sum of squared deviations / n) = 8252 / 8 = 1031.5
    if (stats.getVariance() != 1031.5) {
        unittest::fail("Stats test: getVariance expected 1031.5, got %f", stats.getVariance());
        return false;
    }
 
    unittest::progress(90, "standard deviation");
    if (abs(stats.getStdDev() - 32.11697) > 0.0001) {
        unittest::fail("Stats test: getStdDev expected ~32.11697, got %f", stats.getStdDev());
        return false;
    }
 
    unittest::progress(100, "done");
    return true;
}
 
void Register_Stats_Tests() {
    UnitTestRunner::instance().registerTest("stats", Stats::UnitTest,
        "Statistics: count, sum, average, median, variance, standard deviation", "core");
}
 
 
} // namespace cmlabs