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hjorth

Computes Hjorth parameters (activity, mobility, and complexity) from a signal.

Syntax

function [h0, h1, h2] = hjorth(x, fs)

Description

[H0, H1, H2] = HJORTH(X, FS) computes the three Hjorth parameters from the input signal X sampled at frequency FS. X is the input signal (numeric vector) and FS is the sampling frequency in Hz (positive scalar). The function returns H0 (activity), H1 (mobility), and H2 (complexity) computed using spectral moments of order 0, 2, and 4. The first and second derivatives of the signal are computed automatically using numerical differentiation.

Source Code

View source code

Examples

% Compute Hjorth parameters for a synthetic signal
fs = 1000;  % Sampling frequency
t = 0:1/fs:2;  % Time vector
x = sin(2*pi*10*t) + 0.5*sin(2*pi*50*t) + randn(size(t))*0.1;

% Calculate Hjorth parameters
[h0, h1, h2] = hjorth(x, fs);

% Display results
fprintf('Activity (H0): %.4f\n', h0);
fprintf('Mobility (H1): %.4f Hz\n', h1);
fprintf('Complexity (H2): %.4f\n', h2);

See Also

Module: TOOLS | Last Updated: 2025-09-04