double getError(const vector<SamplePoint> &samples, const VectorN &curCoeff) {
double errSum = 0.0;
for (auto& s : samples) {
double hx = curCoeff.dotProduct(s.features);
errSum += (hx - s.value) * (hx - s.value);
}
return errSum / samples.size();
}
VectorN getErrorGradients(const vector<SamplePoint> &samples, const VectorN &curCoeff) {
VectorN result {(unsigned) curCoeff.vals.size()};
for (unsigned i = 0; i < result.vals.size(); i++) {
// compute d'err/d'theta(i)
double derr = 0.0;
for (auto& s : samples) {
double hx = curCoeff.dotProduct(s.features);
derr += 2.0 * s.features.vals[i] * (hx - s.value);
}
result.vals[i] = derr / samples.size();
}
return result;
}