Source code for neurokit2.complexity.fractal_linelength

# -*- coding: utf-8 -*-
import numpy as np
import pandas as pd

[docs] def fractal_linelength(signal): """**Line Length (LL)** Line Length (LL, also known as curve length), stems from a modification of the :func:`Katz fractal dimension <fractal_katz>` algorithm, with the goal of making it more efficient and accurate (especially for seizure onset detection). It basically corresponds to the average of the absolute consecutive differences of the signal, and was made to be used within subwindows. Note that this does not technically measure the fractal dimension, but the function was named with the ``fractal_`` prefix due to its conceptual similarity with Katz's fractal dimension. Parameters ---------- signal : Union[list, np.array, pd.Series] The signal (i.e., a time series) in the form of a vector of values. Returns ------- float Line Length. dict A dictionary containing additional information (currently empty, but returned nonetheless for consistency with other functions). See Also -------- fractal_katz Examples ---------- .. ipython:: python import neurokit2 as nk signal = nk.signal_simulate(duration=2, sampling_rate=200, frequency=[5, 6, 10]) ll, _ = nk.fractal_linelength(signal) ll References ---------- * Esteller, R., Echauz, J., Tcheng, T., Litt, B., & Pless, B. (2001, October). Line length: an efficient feature for seizure onset detection. In 2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Vol. 2, pp. 1707-1710). IEEE. """ # Sanity checks if isinstance(signal, (np.ndarray, pd.DataFrame)) and signal.ndim > 1: raise ValueError( "Multidimensional inputs (e.g., matrices or multichannel data) are not supported yet." ) # Force to array signal = np.array(signal) # Drop missing values signal = signal[~np.isnan(signal)] # Compute line length ll = np.mean(np.abs(np.diff(signal))) return ll, {}