This function implements the Parameterized form of Temporal Difference (PTD) 
  [1] technique. Use as input data a 3D matrix created grouping NTIMES intensity 
  matrices I(k), 1<=k<=NTIMES

  I(k)=DATA(:,:,k)

  $PTD=\sum\limits_{k=1}^{NTIMES-1} |I(k)-I(k+1)|^P$

  The function is normalized  with the number of elements in the sum.
  Thus, GPTD matrix represents the expected value of absolute difference 
  $|I(k)-I(k+1)|$ for any k value.

  $GPTD=\frac{PTD}{NTIMES-1} \approx E[|I(k)-I(k+1)|^P]$

  References:
  [1] Preeti D. Minz, A.K. Nirala, Intensity based algorithms for biospeckle 
      analysis, Optik - International Journal for Light and Electron Optics, 
      Volume 125, Issue 14, July 2014, Pages 3633-3636, ISSN 0030-4026, 
      http://dx.doi.org/10.1016/j.ijleo.2014.01.083.


  After starting the main routine just type the following command at the
  prompt:
  GPTD = graphptd(DATA);
    
  Input:
  DATA is the speckle data pack. Where DATA is a 3D matrix created grouping NTIMES 
       intensity matrices with NLIN lines and NCOL columns. When N=size(DATA), then
       N(1,1) represents NLIN and
       N(1,2) represents NCOL and
       N(1,3) represents NTIMES.
  P    is a parameter whose value may be positive integer as well as fraction.
  SHOW [Optional] If SHOW is equal to string 'off', then do not plot the result.

  Output:
  GPTD returns the GPTD matrix.


  For help, bug reports and feature suggestions, please visit:
  http://nongnu.org/bsltl

Package: bsltl