FilterChpiParams

Namespace: RTPROCESSINGLIB  ·  Library: DSP Library

#include <dsp/filter_chpi.h>

struct UTILSLIB::FilterChpiParams

Parameters for cHPI notch filtering.

src/examples/ex_dsp_maxwell/main.cpp

const double sFreq = 1000.0;
MatrixXd chpi = MatrixXd::Zero(info.nchan, 4000);
for (int t = 0; t < chpi.cols(); ++t) {
    chpi(meg[0], t) = std::sin(2.0 * kPi * 10.0 * t / sFreq) + std::sin(2.0 * kPi * 83.0 * t / sFreq);
}
const QVector<double> coilFreqs{83.0};
FilterChpiParams chpiParams; // +-2 Hz order-4 notches on the MEG channels only
filterChpi(chpi, info, sFreq, coilFreqs, chpiParams);

---

Example

• Full source: src/examples/ex_dsp_maxwell/main.cpp
• Build target: ex_dsp_maxwell (runs under CTest)
• Data: mne-cpp-test-data

Used in examples

ex_dsp_maxwell

DSP Maxwell filtering: SSS, bad-channel detection, movement compensation, fine calibration and cHPI removal.

src/examples/ex_dsp_maxwell/main.cpp, line 193

const QVector<double> coilFreqs{83.0};
FilterChpiParams chpiParams; // +-2 Hz order-4 notches on the MEG channels only
filterChpi(chpi, info, sFreq, coilFreqs, chpiParams);
double at10 = 0.0;
double at83 = 0.0;
for (int t = 1000; t < 3000; ++t) {
    at10 += chpi(meg[0], t) * std::sin(2.0 * kPi * 10.0 * t / sFreq);
    at83 += chpi(meg[0], t) * std::sin(2.0 * kPi * 83.0 * t / sFreq);
}
ok &= expect(std::fabs(at10 / 1000.0 - 1.0) < 0.05 && std::fabs(at83 / 1000.0) < 0.05,
             QString("filterChpi keeps 10 Hz (%1) and removes the 83 Hz coil (%2)").arg(at10 / 1000.0, 0, 'f', 3).arg(at83 / 1000.0, 0, 'f', 3));

Authors of this file

• Christoph Dinh <christoph.dinh@mne-cpp.org>