DEL2

 

 Five-point discrete Laplacian.

  V = del2(U) is a matrix the same size as U with each element

  equal to the difference between an element of U and the average

  of its four neighbors.  For the "corners" and "edges", only two

  or three neighbors are used.

 

 

  See also GRADIENT1ZKGDQ2, DIFF16RREU2.