nf_stransform

The S-transform or Stockwell transform combines the advantages of both STFT and wavelet methods, and can potentially provide a clearer, more detailed time-frequency representation of M/EEG data compared to either method used alone. The S-transform is calculated using

TF = nf_stransform( data, Fs, plt );

Where data is a 1/2/3D tensor of dimensions channels X time X trials, Fs is the sampling rate of the data in Hz, and plt is 0 or 1 indicating whether or not the user would like a summary plot to be produced following transformation.

Defaults are: plt = 0. Data and Fs are required.

When S-transform is run on the demo synthetic data using

TF = nf_stransform( data, 500 );

We obtain the following result:

../../_images/fig_stransform_synthetic.png

Note that the S-transform has excellent resolution at low-frequencies.

References

Stockwell, R. G., Mansinha, L., & Lowe, R. P. (1996). Localization of the complex spectrum: the S transform. IEEE transactions on signal processing, 44(4), 998-1001.