MATLAB POLYSPACE RELEASE NOTES Manual do Utilizador descarregar pdf (Página 119)

Creating Mesh and Surface Plots

In this section.. .

“About Mesh and Surface Plots” on page 3-63

“Visualizing Functions of Two Va riables” on p age 3-63

AboutMeshandSurfacePlots

MATLAB defines a surface by the z-coo rdinate s of points abov e a grid in the

x-y plane, using straight lines to connect adjacent points. The

mesh and

surf plotting functions display surfaces in three dimensions. mesh produces

wireframe surfaces that color only the lines connecting the defining points.

surf displays both the connecting lines and the faces of the surface in color.

The figure colormap and figure properties determine how MATLAB colors

the surface.

Visualizing Functions of Two Variables

To dis play a function of two variables, z = f (x,y),

1 Generate X and Y matrices consisting of repeated row s and columns,

respectively, over the domain of the function.

2 Use X and Y to evaluate and graph the function.

The

meshgrid function transforms the domain specified by a single vector or

two vectors

x and y into matrices X and Y for use in evaluating functions of

two variables. The rows of

X are copies of the vector x and the columns of

Y are copies of the vector y.

Example — Graphing the sinc Function

This example evaluates and graphs the two-dimensional sinc function,

sin(r)/r, between the x and y directions.

R is the distance from the origin, which

is at the center of the matrix. A dding

eps (a MATLAB command that returns

a small floating-point number) avoids the indeterminate 0/0 at the origin:

[X,Y] = meshgrid(-8:.5:8);

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MATLAB POLYSPACE RELEASE NOTES Manual do Utilizador Página 119