Data gridding.

  ZI = GRIDDATA(X,Y,Z,XI,YI) returns matrix ZI containing elements

  corresponding to the elements of matrices XI and YI and determined by

  interpolation within the 2-D function described by the (usually)

  nonuniformly-spaced vectors (X,Y,Z).



  XI can be a row vector, in which case it specifies a matrix with

  constant columns. Similarly, YI can be a column vector and it 

  specifies a matrix with constant rows. 



  [XI,YI,ZI] = GRIDDATA(X,Y,Z,XI,YI) returns the XI and YI formed

  this way, which are the same as the matrices returned by MESHGRID1Y7VXN8.



  GRIDDATA uses an inverse distance method.



  See also INTERP21R8IYB5, INTERP11R8IXB5.