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SurfaceLaplacian

Namespace: RTPROCESSINGLIB  ·  Library: DSP Library

Python equivalent

mne.preprocessing.compute_current_source_density in MNE-Python.

#include <dsp/surface_laplacian.h>

class UTILSLIB::SurfaceLaplacian

Surface Laplacian / Current Source Density (CSD) transformation.

Computes a reference-free spatial Laplacian of EEG data using spherical spline interpolation (Perrin et al. 1989). This improves spatial resolution by acting as a high-pass spatial filter that enhances local sources and attenuates volume-conducted far-field activity.

Eigen::MatrixX3d pos = ...;  // EEG electrode positions (n_ch × 3)
Eigen::MatrixXd  data = ...; // EEG data (n_ch × n_times)
auto result = SurfaceLaplacian::compute(data, pos);
// result.matData      → CSD-transformed data
// result.matTransform → n_ch × n_ch transformation matrix

Static Methods​

compute(matData, matPositions, dLambda2, iStiffness, iNLegendreTerms, dSphereRadius)​

Compute the surface Laplacian (CSD) transformation.

Parameters:

  • matData : const Eigen::MatrixXd & EEG data matrix (n_channels × n_times).

  • matPositions : const Eigen::MatrixX3d & Electrode positions in 3D (n_channels × 3), in head coordinates.

  • dLambda2 : double Regularization parameter (default 1e-5).

  • iStiffness : int Spline stiffness parameter (default 4).

  • iNLegendreTerms : int Number of Legendre terms to evaluate (default 50).

  • dSphereRadius : double Sphere radius in metres; if <= 0, fitted from positions (default -1).

Returns:

  • SurfaceLaplacianResult — SurfaceLaplacianResult with transformed data and transform matrix.

computeTransform(matPositions, dLambda2, iStiffness, iNLegendreTerms, dSphereRadius)​

Compute only the CSD transformation matrix (without applying to data).

Parameters:

  • matPositions : const Eigen::MatrixX3d & Electrode positions in 3D (n_channels × 3).

  • dLambda2 : double Regularization parameter (default 1e-5).

  • iStiffness : int Spline stiffness parameter (default 4).

  • iNLegendreTerms : int Number of Legendre terms (default 50).

  • dSphereRadius : double Sphere radius; if <= 0, fitted from positions.

Returns:

  • Eigen::MatrixXd — Transformation matrix (n_channels × n_channels).

Authors of this file​