--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/+utils/@helper/time_data_worsener.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,86 @@
+% 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
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