Usage: 3dDTeig [options] dataset
Computes eigenvalues and eigenvectors for an input dataset of
 6 sub-bricks Dxx,Dxy,Dyy,Dxz,Dyz,Dzz (lower diagonal order).
 The results are stored in a 14-subbrick bucket dataset.
 The resulting 14-subbricks are

The output is a bucket dataset.  The input dataset
may use a sub-brick selection list, as in program 3dcalc.
  -prefix pname = Use 'pname' for the output dataset prefix name.

  -datum type = Coerce the output data to be stored as the given type
    which may be byte, short or float. [default=float]

  -sep_dsets = save eigenvalues,vectors,FA,MD in separate datasets

  -uddata = tensor data is stored as upper diagonal
            instead of lower diagonal

 Mean diffusivity (MD) calculated as simple average of eigenvalues.
 Fractional Anisotropy (FA) calculated according to Pierpaoli C, Basser PJ.
 Microstructural and physiological features of tissues elucidated by
 quantitative-diffusion tensor MRI, J Magn Reson B 1996; 111:209-19

This program accepts datasets that are modified on input according to the
following schemes:
  'r1+orig[3..5]'                                    {sub-brick selector}
  'r1+orig<100..200>'                                {sub-range selector}
  'r1+orig[3..5]<100..200>'                          {both selectors}
  '3dcalc( -a r1+orig -b r2+orig -expr 0.5*(a+b) )'  {calculation}
For the gruesome details, see the output of 'afni -help'.

++ Compile date = Aug 10 2020 {AFNI_20.2.11:linux_ubuntu_16_64}