Spectrum Spectrum::add(double coeff_this, double coeff, const Spectrum & rhs) const {
assert(elems.size()==rhs.elems.size());
const size_t n = elems.size();
Spectrum result(n);
for(size_t i=0; i<n; ++i){
result.elems[i] = coeff_this * elems[i] + coeff * rhs.elems[i];
}
const double ct2 = coeff_this * coeff_this;
const double c2 = coeff * coeff;
for(size_t i=0; i<n; ++i){
for(size_t j=0; j<n; ++j){
result.cov_(i,j) = ct2 * cov_(i,j) + c2 * rhs.cov_(i, j);
}
}
return result;
}
