Basics of MATLAB and Beyond

z = 5*ones(3,3)z =5 5 55 5 55 5 5>> surf(x,y,z)0 −1But, of course, the z values need not be constant:>> z = [[4; 5; 6] [4.5; 5; 5.5] [4.9; 5; 5.1]]z =4.0 4.5 4.95.0 5.0 5.066.0 5.5 5.15.5>> surf(x,y,z)565.554.53 44.521013 4210−101Other graphics functions can also handle nonrectangular grids. Here isan example using the contour function:35.8cs = contour(x,y,z,’k’);clabel(cs)i = [1 4 7 9 6 3 1];hold onplt(x(i),y(i),’:’)2.521.510.55.654.85.44.2 4.4 4.65.20−1 −0.5 0 0.5 1The contour levels are labelled using the clabel command, and theregion defined by the x and y points is outlined by the dotted line. Thecontours that the labels refer to are marked by small plus signs ‘+’. Theoutline around the bent domain is drawn using the x and y matricesindexed using the vector i. The vector i extracts the appropriate pointsfrom the x and y matrices using the columnar indexing described in section3.4 on page 9. The other surface graphics functions—mesh, surfl,surfc, and contourf—can handle such nonrectangular grids equallywell. The image and imagesc functions assume equally spaced rectangulargrids and cannot handle anything else. (The pcolor functiondraws a surface and sets the view point to directly overhead, so it is notdiscussed separately.)Let us now do another example of a surface defined over a nonrectangulargrid. We want to define a set of points that cover the semi-c○ 2000 by CRC Press LLC