Matlab中Sphere函数的轮廓图输入错误 [英] Input error in Contour plot of a Sphere Function in Matlab

问题描述

我试图用等高线绘制一个球体函数，但是我仍然收到以下错误。

 错误使用==> Z必须大小为2x2或更大。 
  

错误是在这一行代码：

轮廓（X1，X2，Z）;

这是球体函数：

  function ph = sphere（x）
 ph = sum（x。* x，2）; 
 end 
  

以下是使用轮廓图绘制球体的代码：

  min = -25; 
 max = 25; 
 h = 25; 
 c =空格（min，max，h）; ％创建网格
 [X1，X2] = meshgrid（c，c）; ％创建网格
 
 Z =球（X1，X2）; 
 
数字; 
 icontour（X1，X2，Z）; 
  

我希望Z返回至少一个2x2矩阵。 Z应该是球的高度，X1是x轴，X2是y轴。

如何消除错误？

解决方案

您的中的问题是 sum 球体功能。而 X1 和 X2 是 25x25 矩阵， ph 是一个 25x1 矢量。尝试这样：

 函数ph = sphere（x）
 
 ph = x。* x; 
  

在这种情况下，您的价值 ph 将与您的网格变量相同。

修改

如果您使用更新的方法：

  Z = arrayfun（@sphere，X1）; 
  

您将获得不变的行，因为您只需将X1传递到您的球体函数。在这种情况下，与...相同：

  ph = sum（x。^ 2,2）; 
  

要获得一个球体，您要传递两个参数， X1 和 X2 ：

  function ph = sphere x1，x2）
 ph = sum（x1。* x2,2）; 
 end 
  

并打电话：

  Z = arrayfun（@sphere，X1，X2）; 
  

如果你打电话给你修改的函数，你会得到这个结果：

编辑2

注意：如果您在某个地方使用球体在你的脚本中，你必须更新每个调用它以包括两个输入参数。

编辑3

根据您实施此代码的细节，我会建议不要使用 sphere 作为函数的名称，因为 Matlab自己的这个名字的功能。

I am trying to plot a sphere function using contour plot, but I keep getting the following error.

??? Error using ==> Z must be size 2x2 or greater.

Error in is at this line of code:

contour(X1, X2, Z);

Here is the sphere function:

function ph = sphere(x)
         ph = sum(x.*x, 2);
end

Here is the code to plot the sphere using contour plot:

min = -25;
max = 25;
h = 25;
c= linspace(min, max, h); % Create the mesh
[X1, X2] = meshgrid(c, c); % Create the grid

Z = sphere(X1,X2);

figure;
icontour(X1, X2, Z);

I expect Z to return at least a 2x2 matrix. Z is supposed to be the height of the sphere and X1 is the x-axis and X2 is the y-axis.

How can I eliminate the error?

解决方案

The problem is sum in your sphere function. While X1 and X2 are 25x25 matrices, phis a 25x1vector. Try this:

function ph = sphere(x)

ph = x.*x;  

In this case, your value ph will be of the same dimenion as your grid variables.

Edit

If you use your updated approach:

Z = arrayfun(@sphere, X1);

You will get constant lines because you just pass X1 to your spheres function. Which, in that case is the same as:

ph = sum(x.^2,2);  

To get a sphere, you want to pass both arguments, X1 and X2:

function ph = sphere(x1,x2)
     ph = sum(x1.*x2, 2);
end  

And call:

Z = arrayfun(@sphere, X1, X2);

If you call your modified function like that, you'll get this result:

Edit 2

ATTENTION: If you are using sphere somewhere else in your script, you have to update each call to it to include two input arguments.

Edit 3

Depending on how carefully you implement this code, I would advise against using sphere as a name for a function, because of Matlab's own function with that name.

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