Graphics Programs Reference

In-Depth Information

x 294x1 2352 double array

xi 50x50 20000 double array

xiv 1x50 400 double array

y 294x1 2352 double array

yi 50x50 20000 double array

yiv 1x50 400 double array

z 294x1 2352 double array

zi 50x50 20000 double array

Grand total is 8711 elements using 68314 bytes

We now have three new matrix variables
xi
,
yi
, and
zi
that correspond

to the interpolated data. We make a plot of the original data and the

interpolated surface:

plot3(x,y,z,'o')

hold on

surf(xi,yi,zi)

colormap(autumn)

axis tight

Where the points of the rectangular interpolation grid lie outside the

convex hull defined by the data, the values are interpolated as
NaN
and

are omitted from the surface plot. There are a variety of ways to do the

interpolation; these are described in the help entry for
griddata
.We

can use the interpolated data to plot a contour map of the seamount:

contour(xi,yi,zi)

36.2 Triangular Gridding

matlab comes equipped with the following functions for use in defining

triangular grids:

griddata delaunay trimesh dsearch

convhull voronoi

trisurf tsearch

The idea is that for any set of points (distinct and with no colinear

subsets) in two dimensions, a set of triangles can be defined such that

(1) no points lie within any triangle's circumcircle and (2) the set com-

pletely covers the convex hull of the points. This idea is illustrated in this