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FiffChInfo

Namespace: FIFFLIB  ·  Library: FIFF Library

#include <fiff/fiff_ch_info.h>

class FIFFLIB::FiffChInfo

Per-channel FIFF descriptor: identifiers, kind, calibration, coil type, channel-frame coil position and SI unit.

Holds the exact field set of the on-disk fiffChInfoRec: scanno, logno, kind, range, cal, coil_type, the embedded FiffChPos coil location, unit and unit_mul. The ch_name string lives next to the record because the FIFF stream stores it as a separate FIFF_CH_NAME tag in modern files.

src/examples/ex_fiff_api/main.cpp
QFile rawFile(dir + "/sample_audvis_trunc_raw.fif");
FiffRawData raw(rawFile);        // reads the measurement info, raw data is read on demand
const FiffInfo& info = raw.info; // channels, sampling rate, bads, projectors, digitizer, transforms
const FiffChInfo& first = info.chs[0];
const RowVectorXi megPicks = info.pick_types(true, false, false, QStringList(), info.bads); // good MEG channels

Public Methods​

FiffChInfo()​

Constructs the channel info descriptor.

FiffChInfo(p_FiffChInfo)​

Copy constructor.

Parameters:

  • p_FiffChInfo : const FiffChInfo & Channel Info descriptor which should be copied.

operator=(other)​

Copy assignment.

Every member has value semantics, so the compiler-generated member-wise assignment is correct. It is declared explicitly because declaring a copy constructor and/or a destructor deprecates the implicitly generated one.

Parameters:

  • other : const FiffChInfo & Object to assign from.

Returns:

~FiffChInfo()​

Destroys the channel info descriptor.

isValidEeg()​

Check whether this channel has a valid EEG electrode position.

A channel is a valid EEG channel if its kind is FIFFV_EEG_CH, its electrode position is not at the origin, and its coil type is not FIFFV_COIL_NONE.

Returns:

  • bool — true if this is a valid EEG channel with proper electrode location.

Static Methods​

storageSize()​

Size of the old struct (fiffChInfoRec) 20int + 16 = 204 + 16 = 96.

Returns:

  • qint32 — the size of the old struct fiffChInfoRec.

checkEegLocations(chs, nch)​

Check that all EEG channels in the list have reasonable (non-origin) locations.

Formerly mne_check_chinfo (MNE C).

Parameters:

  • chs : const QList< FiffChInfo > & The list of channel info structures to check.

  • nch : int The number of channels to check.

Returns:

  • bool — true if all EEG channels have valid locations, false otherwise.

Example​

Used in examples​

ex_fwd_api​

Forward library: coil definitions, BEM and sphere models, field maps and forward solutions.

src/examples/ex_fwd_api/main.cpp, line 100
QFile rawFile(data + "/MEG/sample/sample_audvis_trunc_raw.fif");
const FiffRawData raw(rawFile);
QList<FiffChInfo> meg;
QList<FiffChInfo> goodMeg;
QList<FiffChInfo> eeg;
for (const FiffChInfo& ch : raw.info.chs) {
    if (ch.kind == FIFFV_MEG_CH) {
        meg << ch;
        if (!raw.info.bads.contains(ch.ch_name)) {
            goodMeg << ch;
        }
    } else if (ch.kind == FIFFV_EEG_CH) {
        eeg << ch;
    }

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 76
        const FiffChInfo& ch = info.chs[meg[k]];
        const Vector3d r = ch.chpos.r0.cast<double>() - pos;
        const double d = r.norm();
        const Vector3d dipole = (3.0 * r * r.dot(moment) / (d * d) - moment) / (d * d * d);
        b(k) = ch.chpos.ez.cast<double>().normalized().dot(dipole + uniform);
    }
    return b;
}

ex_fiff_api​

FIFF library: measurement info, channels, digitizer, transforms, projectors, covariance, events,.

src/examples/ex_fiff_api/main.cpp, line 109
QFile rawFile(dir + "/sample_audvis_trunc_raw.fif");
FiffRawData raw(rawFile);        // reads the measurement info, raw data is read on demand
const FiffInfo& info = raw.info; // channels, sampling rate, bads, projectors, digitizer, transforms
const FiffChInfo& first = info.chs[0];
const RowVectorXi megPicks = info.pick_types(true, false, false, QStringList(), info.bads); // good MEG channels
// mne.io.read_raw_fif: 376 channels at 300.307 Hz, bads MEG 2443 + EEG 053, 4 projectors
ok &= expect(info.nchan == 376 && near(info.sfreq, 300.3074951171875) && info.bads == QStringList({"MEG2443", "EEG053"}) && info.projs.size() == 4 && megPicks.size() == 305 && raw.first_samp == 12900 && raw.last_samp == 18906,
             "FiffInfo: 376 channels at 300.307 Hz, 2 bads, 4 projectors, 305 good MEG channels");
// ch 0: MEG 0113, planar gradiometer 3012 at (-0.1066, 0.0464, -0.0604) m, cal 3.16e-9
ok &= expect(first.ch_name == "MEG0113" && first.kind == FIFFV_MEG_CH && first.chpos.coil_type == FIFFV_COIL_VV_PLANAR_T1 && (first.chpos.r0 - Vector3f(-0.1066f, 0.0464f, -0.0604f)).norm() < 1e-6f && near(first.cal, 3.1600000394149674e-09),
             "FiffChInfo/FiffChPos: MEG0113 is a 3012 planar gradiometer at (-0.1066, 0.0464, -0.0604) m");

Also used in ex_interpolation, ex_inv_hpi, ex_dsp_artifacts, ex_dsp_rt.

Authors of this file​