== MS_checkC

 MS_CHECKC - check consistency of a stiffness matrix against various criteria

 // Part of MSAT - The Matlab Seismic Anisotropy Toolkit //

 [ isgood ] = MS_checkC( C,... )

	Inputs:
     C = Stiffness tensor for checking

  Outputs:
     isgood = 1 for OK

  Options:
     Various checks can be disabled/enabled by specifying extra options:
        'fast' - run a minimal set of checks (size and type only)
        'warn' - warn only on more sophisticated errors than size/type
        'nosymchk' - disable upper, lower symmetry checking
        'nozerochk' - disable top left / trace zero checking 
        'nopdefchk' - disable positive definiteness check 
 
     Various control parameters can be set by adding parameter,value pairs 
     to the arguments
        'thresh',x - set numerical threshold for zero to x (default = 1e-6)

  Notes:
  Currently, the following properties of the input elastic stiffness
  matrix, C, are tested: (1) The maxtrix must be of rank 2 and size (6,6).
  (2) The matrix must be symmetrical along the leading diagonal (i.e. 
  the major symmetry of the elastic constants tensor, Cijkl == Cklij, must
  be present). (3) The matrix must be positive-definite and be none zero
  in the leading diagonal and top left corner.

