Contour computation.

  CONTOURC calculates the contour matrix C for use by CONTOURXAOYTS

  to draw the actual contour plot.

  C = CONTOURC(Z) computes the contour matrix for a contour plot

  of matrix Z treating the values in Z as heights above a plane.

  C = CONTOURC(X,Y,Z), where X and Y are vectors, specifies the X- 

  and Y-axes for the contour computation.

  CONTOURC(Z,N) and CONTOURC(X,Y,Z,N) compute N contour lines, 

  overriding the default automatic value.

  CONTOURC(Z,V) and CONTOURC(X,Y,Z,V) compute LENGTH21WMMAG(V) contour 

  lines at the values specified in vector V.


  The contour matrix C is a two row matrix of contour lines. Each

  contiguous drawing segment contains the value of the contour, 

  the number of (x,y) drawing pairs, and the pairs themselves.  

  The segments are appended end-to-end as



      C = [level1 x1 x2 x3 ... level2 x2 x2 x3 ...;

           pairs1 y1 y2 y3 ... pairs2 y2 y2 y3 ...]