function find_cmd_and_vel( the_data )
% find static commands and corresponding steady state velocities.

% for converting encoder speeds to radians/second
  full_revolution = 11*4*64*30;

% spikes in the derivative of the command will tell us when the command changes
  diff_command = diff(the_data(:,4));

% low pass filter the velocities to get rid of PicoEncoder noise artifact
  [B,A] = butter(2,0.01);
% convert to radians/second
  left_vel = filtfilt(B,A,the_data(:,3))/full_revolution;
  right_vel = filtfilt(B,A,the_data(:,6))/full_revolution;

% plot stuff
  figure(2);
  hold off
  plot(left_vel);
  title( 'left velocity (filtered and radians/second)' );
  xlabel( 'samples' )
  ylabel( 'radians/second' )
  figure(3);
  hold off
  plot(right_vel);
  title( 'right velocity (filtered radians/second)' );
  xlabel( 'samples' )
  ylabel( 'radians/second' )
  figure(4);
  hold off
  plot(the_data(:,3));
  title( 'left velocity (raw)' );
  xlabel( 'samples' )
  ylabel( 'encoder_counts/second' )
  figure(5);
  hold off
  plot(the_data(:,6));	     
  title( 'right velocity (raw)' );
  xlabel( 'samples' )
  ylabel( 'encoder_counts/second' )
	       
  % back up from the command change - this avoids filter ringing artifact
  % https://en.wikipedia.org/wiki/Ringing_artifacts
  shift = 250;

  % set up a variable that helps us from being fooled by weird stuff
  last_jump_index = 0;

  % open the file to save the data in (zzz, rename it as you wish)
  fid = fopen( 'zzz', 'w' );

  for i = 1:length( diff_command )
    if abs( diff_command( i ) ) > 0.1 % test for command discontinuity
      if ( i - shift ) < 1 % if the shift backwards goes off the start of the
        continue;          % data
      end
      if ( i - shift - last_jump_index ) < 900 % real command changes happen
        continue;                              % at least 1 second apart
      end
      % print data
      fprintf( 1, "%8d %4d %14.6f %14.6f\n", i - shift, ...
	       the_data( i - shift, 4 ), ...
	       left_vel( i - shift ), right_vel( i - shift ) );
      % save data
      fprintf( fid, "%8d %4d %14.6f %14.6f\n", i - shift, ...
	       the_data( i - shift, 4 ), ...
	       left_vel( i - shift ), right_vel( i - shift ) );
      % update this variable
      last_jump_index = i - shift;
    end
  end
  if ( i - shift - last_jump_index ) > 900 % real command changes happen    
                                             % at least 1 second apart
    % print data
    fprintf( 1, "%8d %4d %14.6f %14.6f\n", i - shift, ...
             the_data( i - shift, 4 ), ...
             left_vel( i - shift ), right_vel( i - shift ) );
    % save data
    fprintf( fid, "%8d %4d %14.6f %14.6f\n", i - shift, ...
             the_data( i - shift, 4 ), ...
             left_vel( i - shift ), right_vel( i - shift ) );
  end
  % close the file
  fclose( fid );
end