%
% PURPOSE: Backdifference time to reveal dropouts.
% AUTHOR: Rob McEwen
% DATE: 98/10/16
%
  sz = size(data1);
  dim = sz(1)-1;
  bdVel = data1(2:sz(1),vel) - data1(1:dim,vel);
  bdTime = data1(2:sz(1),time) - data1(1:dim,time);
  velDrop  = 0;
  timeDrop = 0;
  for i = 1 : dim
    if(bdVel(i) ~= 0)  velDrop  = velDrop + 1;end
    if(bdTime(i) ~= 0) timeDrop = timeDrop + 1;end
  end
  freq = 1/(data1(3,time)-data1(2,time))
  velFreq = freq* (velDrop)/(dim)
  timeFreq = freq* (timeDrop)/(dim)
  disp([' Velocity sampling freq is ' num2str(velFreq)])
  disp([' Time sampling freq is ' num2str(timeFreq)])
  figure(4)
  clf
  plot(data1(2:sz,time),bdVel);
  grid on
