编程：MATLAB中的Peaks函数是什么

为了方便测试立体绘图，MATLAB提供了一个peaks函数，可产生一个凹凸有致的曲面，包含了三个局部极大点及三个局部极小点，其方程式为：

要画出此函数的最快方法即是直接键入

peaks：

z = 3*(1-x).^2.*exp(-(x.^2) – (y+1).^2) …

– 10*(x/5 – x.^3 – y.^5).*exp(-x.^2-y.^2) …

– 1/3*exp(-(x+1).^2 – y.^2)

我们亦可对peaks函数取点，再以各种不同方法进行绘图。

——————————————————————-

MATLAB中的帮助信息：

<span style="font-family: &quot;Courier New&quot;color: blue;font-size: 10pt" lang="EN-US"></span>

1	<span style="font-family: "Courier New"color: blue;font-size: 10pt" lang="EN-US"></span>

<span style="font-family: &quot;Courier New&quot;color: blue;font-size: 10pt" lang="EN-US"></span>
<span style="font-family: &quot;Courier New&quot;color: blue;font-size: 10pt" lang="EN-US"><span style="color: #000000"><span style="font-family: 宋体">PEAKS  A sample function of two variables.
    PEAKS is a function of two variables, obtained by translating and
    scaling Gaussian distributions, which is useful for demonstrating
    MESH, SURF, PCOLOR, CONTOUR, etc.
    There are several variants of the calling sequence:
 
        Z = PEAKS;
        Z = PEAKS(N);
        Z = PEAKS(V);
        Z = PEAKS(X,Y);
 
        PEAKS;
        PEAKS(N);
        PEAKS(V);
        PEAKS(X,Y);
 
        [X,Y,Z] = PEAKS;
        [X,Y,Z] = PEAKS(N);
        [X,Y,Z] = PEAKS(V);
 
    The first variant produces a 49-by-49 matrix.
    The second variant produces an N-by-N matrix.
    The third variant produces an N-by-N matrix where N = length(V).
    The fourth variant evaluates the function at the given X and Y,
    which must be the same size.  The resulting Z is also that size.
 
    The next four variants, with no output arguments, do a SURF
    plot of the result.
 
    The last three variants also produce two matrices, X and Y, for
    use in commands such as PCOLOR(X,Y,Z) or SURF(X,Y,Z,DEL2(Z)).
 
    If not given as input, the underlying matrices X and Y are
        [X,Y] = MESHGRID(V,V)
    where V is a given vector, or V is a vector of length N with
    elements equally spaced from -3 to 3.  If no input argument is
    given, the default N is 49.</span></span></span>

PEAKS A sample function of two variables.

PEAKS is a function of two variables, obtained by translating and

scaling Gaussian distributions, which is useful for demonstrating

MESH, SURF, PCOLOR, CONTOUR, etc.

There are several variants of the calling sequence:

Z = PEAKS;

Z = PEAKS(N);

Z = PEAKS(V);

Z = PEAKS(X,Y);

PEAKS;

PEAKS(N);

PEAKS(V);

PEAKS(X,Y);

[X,Y,Z] = PEAKS;

[X,Y,Z] = PEAKS(N);

[X,Y,Z] = PEAKS(V);

The first variant produces a 49-by-49 matrix.

The second variant produces an N-by-N matrix.

The third variant produces an N-by-N matrix where N = length(V).

The fourth variant evaluates the function at the given X and Y,

which must be the same size. The resulting Z is also that size.

The next four variants, with no output arguments, do a SURF

plot of the result.

The last three variants also produce two matrices, X and Y, for

use in commands such as PCOLOR(X,Y,Z) or SURF(X,Y,Z,DEL2(Z)).

If not given as input, the underlying matrices X and Y are

[X,Y] = MESHGRID(V,V)

where V is a given vector, or V is a vector of length N with

elements equally spaced from -3 to 3. If no input argument is

given, the default N is 49.

<span style="font-family: &quot;Courier New&quot;color: blue;font-size: 10pt" lang="EN-US"><span style="color: #000000"><span style="font-family: 宋体">    Reference page in Help browser
       doc peaks</span></span></span>

1 2	<span style="font-family: "Courier New"color: blue;font-size: 10pt" lang="EN-US"><span style="color: #000000"><span style="font-family: 宋体"> Reference page in Help browser doc peaks</span></span></span>

<span style="font-family: &quot;Courier New&quot;color: blue;font-size: 10pt" lang="EN-US"><span style="color: #000000"><span style="font-family: 宋体"> 
z =  3*(1-x).^2.*exp(-(x.^2) - (y+1).^2) ...
   - 10*(x/5 - x.^3 - y.^5).*exp(-x.^2-y.^2) ...
   - 1/3*exp(-(x+1).^2 - y.^2) </span></span></span>

z = 3*(1-x).^2.*exp(-(x.^2) - (y+1).^2) ...

- 10*(x/5 - x.^3 - y.^5).*exp(-x.^2-y.^2) ...

- 1/3*exp(-(x+1).^2 - y.^2)

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