noise.m

function signal = noise (frames, epochs, srate, pulse, position)

% function signal = noise (frames, epochs, srate)
%
% Function generates noise with the power spectrum of human EEG
% Inputs:
%  frames - number of signal frames per each trial
%  epochs - number of simulated trials
%  srate - sampling rate of simulated signal
% Output:
%  signal - simulated EEG signal; vector: 1 by frames*epochs containing concatenated trials
% Implemented by: Rafal Bogacz and Nick Yeung, Princeton Univesity, December 2002

load meanpower  
sumsig = 50;	%number of sinusoids from which each simulated signal is composed of

signal = zeros (1, epochs * frames);
for trial = 1:epochs
   freq=0;
   range = [(trial-1)*frames+1:trial*frames];
   for i = 1:sumsig
      freq = freq + (4*rand(1));
      freqamp = meanpower(min (ceil(freq), 125)) / meanpower(1);
      phase = rand(1)*2*pi;
      signal (range) = signal (range) + sin ([1:frames]/srate*2*pi*freq + phase) * freqamp;
   end
end

if pulse
    for i = 1:epochs-1
        signal(i*frames+position) = signal(i*frames+position) - 2500;
    end
end