sphara.h File Reference

SPatial HARmonic Analysis (SPHARA) spatial-filter projector assembly. More...

#include "dsp_global.h"
#include <Eigen/Core>

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Namespaces
namespace	UTILSLIB
	Shared utilities (I/O helpers, spectral analysis, layout management, warp algorithms).

Functions
DSPSHARED_EXPORT Eigen::MatrixXd	UTILSLIB::makeSpharaProjector (const Eigen::MatrixXd &matBaseFct, const Eigen::VectorXi &vecIndices, int iOperatorDim, int iNBaseFct, int iSkip=0)

Detailed Description

SPatial HARmonic Analysis (SPHARA) spatial-filter projector assembly.

SPDX-License-Identifier: BSD-3-Clause Copyright (c) 2026 MNE-CPP Authors

Author

Christoph Dinh chris.nosp@m.toph.nosp@m..dinh.nosp@m.@mne.nosp@m.-cpp..nosp@m.org

Since

2.0.0

Date

March 2026

SPHARA represents a discrete EEG / MEG sensor montage as a triangulated manifold and decomposes its spatial degrees of freedom into the eigen- functions of the discrete Laplace–Beltrami operator on that mesh. Truncating the expansion at the lowest iNBaseFct harmonics suppresses high spatial frequencies that are dominated by sensor noise and reference artefacts, giving a denoising / smoothing projector that is the spatial-domain analogue of a low-pass filter.

makeSpharaProjector assembles the dense (iOperatorDim × iOperatorDim) projection matrix from a stack of pre-computed basis functions. The vecIndices argument maps the rows of the basis-function matrix back to channel indices in the full data matrix, and iSkip lets a single basis set be reused for interleaved sensor triplets such as the Neuromag / MEGIN VectorView gradiometer pairs.

Reference: Graichen U. et al., NeuroImage 86 (2014) 467–478.

Definition in file sphara.h.