Contour Plot for Scattered Data

TRICONTOUR(TRI,X,Y,Z,N) draws scalar N contour lines treating the values in Z as heights above a plane. TRI,X,Y,and Z define a triangulation where the triangles are defined by the M-by-3 face matrix TRI, such as that returned by DELAUNAY. Each row of TRI contains indices into the X,Y, and Z vertex vectors to define a single triangular face. Contours are computed directly from the triangulation rather than interpolating back to a cartesian grid using GRIDDATA.
TRICONTOUR(TRI,X,Y,Z,V) draws length(V) contour lines at the values specified in vector V.
TRICONTOUR(TRI,X,Y,Z,[v v]) draws a single contour line at the level v.
[C,H] = TRICONTOUR(...) returns contour matrix C as described in CONTOURC and a vector of handles H to the created patch objects.
H can be used to set patch properties.
CLABEL(C) or CLABEL(C,H) labels the contour levels.