+
−% TIME_DATA_WORSENER introduces missing points and/or unvenly sampling time
+
−% inside time series
+
−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
−%
+
−% FUNCTION:    time_data_worsener
+
−%
+
−% DESCRIPTION: TIME_DATA_WORSENER introduces missing points and/or unvenly
+
−%              sampling times inside time series
+
−%
+
−% CALL:        [t, y] = time_data_worsener(t, y, miss_fraction, shift_fraction, shift_range);
+
−%
+
−% INPUTS:      t              vector of evenly sampled time values (in s)
+
−%              y              vector of evenly sampled y values (in arb units)
+
−%              miss_fraction  fraction of the total point to be skipped
+
−%              shift_fraction fraction of the total point to be shifted
+
−%              shift_range    selection range for shifting the time points (in s)                             
+
−%
+
−% OUTPUTS:     t              vector of unevenly time values
+
−%              y              vector of unevenly sampled y values
+
−%
+
−% EXAMPLES:    [t1,y1] = time_data_worsener(t, y, 0.5, 0, [0 0]);
+
−%              [t1,y1] = time_data_worsener(t, y, 0, 0.1, [-0.05 0.05]);
+
−%              [t1,y1] = time_data_worsener(t, y, 0.1, 0.5, [0 0.01]);
+
−%
+
−% VERSION:     $Id: time_data_worsener.m,v 1.1 2009/01/25 16:06:30 mauro Exp $
+
−%
+
−% HISTORY:     25-01-2009 Hueller
+
−%                 Creation
+
−%
+
−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
−
+
−function [t,y] = time_data_worsener(t, y, miss_fraction, shift_fraction, shift_range)
+
−  
+
−  % Initial checks
+
−  if isempty(t) || isempty(y)
+
−    error('Need to operate on non empty data vectors!')
+
−  end
+
−  
+
−  if length(y) ~= length(t)
+
−    error('t and y vector should have the same lenghts!');
+
−  end
+
−  
+
−  if miss_fraction > 1 || miss_fraction < 0
+
−    error('Missing points fraction f must fulfil 0 <= f <= 1!');
+
−  end
+
−  
+
−  if shift_fraction > 1 || shift_fraction < 0
+
−    error('Shifted points fraction f must fulfil 0 <= f <= 1!');
+
−  end
+
−  
+
−  if length(shift_range) < 2
+
−    error('Please input the shifting freqency range []');
+
−  end
+
−  
+
−  %% Remove an amount of points corresponding to the fractional amount input by user
+
−  
+
−  % Calculate the orginal data vector length
+
−  N_points = length(t);
+
−   
+
−  % Calculate the number of data points to keep
+
−  N_keep = round((1 - miss_fraction) * N_points);
+
−  
+
−  % Randonmly calculate the index of the data to keep
+
−  keep_index = sort(randsample(N_points, N_keep));
+
−  
+
−  % Extract the data from time and y vector
+
−  t = t(keep_index);
+
−  y = y(keep_index);
+
−  
+
−  %% Shift the remaining points by a random amount within the input range
+
−  N_points = length(t);
+
−  
+
−  %  Calculate the number of points to shift
+
−  N_shift = round(shift_fraction * N_points);
+
−  
+
−  % Randonmly calculate the index of the data not to shift
+
−  shift_index = sort(randsample(N_points, N_shift));
+
−  
+
−  % Randomly calculate the delay (positive or negative) and apply it  
+
−  shifts = shift_range(1) + (shift_range(2) - shift_range(1))*rand(N_shift, 1);
+
−  
+
−  for kk = 1 : N_shift    
+
−    t(shift_index(kk)) =  t(shift_index(kk)) + shifts(kk);
+
−  end
+
−  
+
−end