{

auto file_mzML = OPENMS_DOC_PATH + String("/code_examples/data/Tutorial_GaussFilter.mzML");

MSExperiment spectra;

// load mzML from code examples folder

FileHandler().loadExperiment(file_mzML, spectra);

// iterate over map and output MS2 precursor information

for (auto s_it = spectra.begin(); s_it != spectra.end(); ++s_it)

{

// we are only interested in MS2 spectra so we skip all other levels

if (s_it->getMSLevel() != 2) continue;

// get a reference to the precursor information

const MSSpectrum& spectrum = *s_it;

const vector<Precursor>& precursors = spectrum.getPrecursors();

// size check & throw exception if needed

if (precursors.empty()) throw Exception::InvalidSize(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION, precursors.size());

// get m/z and intensity of precursor

double precursor_mz = precursors[0].getMZ();

float precursor_int = precursors[0].getIntensity();

// retrieve the precursor spectrum (the most recent MS1 spectrum)

PeakMap::ConstIterator precursor_spectrum = spectra.getPrecursorSpectrum(s_it);

double precursor_rt = precursor_spectrum->getRT();

// output precursor information

std::cout << " precursor m/z: " << precursor_mz

<< " intensity: " << precursor_int

<< " retention time (sec.): " << precursor_rt

<< std::endl;

}

return 0;