在 matlab 中表示向量值函数

发布于 2024-11-29 07:45:21 字数 523 浏览 2 评论 0原文

将以下简短的 python/numpy 代码转换为 matlab 的最佳方法是什么

from numpy import *

F = lambda x, y: (-y, x)

points = array(meshgrid([1,2,3], [4,5,6,7]))
vx, vy = F(*points)
print vx, vy

在上面的代码中，F 旨在表示向量值速度场。具体来说，向量值函数应该使用单元格来表示，还是有更好的方法来实现？

第一次尝试翻译上面的代码：

F = @(x,y) {-y, x};

[X, Y] = meshgrid(1:3, 4:7);
rslt = F(X, Y); 
[vx, vy] = rslt{:};

有更优雅的方法吗？例如，匿名函数是否可以返回多个值，以便可以像这样 [vx, vy] = F(X,Y); 那样调用它，而不必定义一个中间 rslt 变量？

原文

What is the best way to translate the following brief python/numpy code to matlab

from numpy import *

F = lambda x, y: (-y, x)

points = array(meshgrid([1,2,3], [4,5,6,7]))
vx, vy = F(*points)
print vx, vy

In the code above, F is intended to represent a vector-valued velocity field. Specfically, should a vector-valued function be represented using cells, or is there a better way to do it?

A first attempt to translate the above code:

F = @(x,y) {-y, x};

[X, Y] = meshgrid(1:3, 4:7);
rslt = F(X, Y); 
[vx, vy] = rslt{:};

Is there a more elegant way to do it? For example, could the anonymous function return more than one value so that one can call it like this [vx, vy] = F(X,Y); rather than having to define an intermediate rslt variable?

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梦萦几度 2024-12-06 07:45:21

您可以将其分为两个函数：

%# each is a function of two variables
Fx = @(x,y) -y;
Fy = @(x,y) x;

[X,Y] = meshgrid(1:3, 4:7);
vx = Fx(X,Y);
vy = Fy(X,Y);

You could split it into two functions:

%# each is a function of two variables
Fx = @(x,y) -y;
Fy = @(x,y) x;

[X,Y] = meshgrid(1:3, 4:7);
vx = Fx(X,Y);
vy = Fy(X,Y);

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離人涙 2024-12-06 07:45:21

内联函数不能返回多个输出，这似乎很奇怪。有几种可能的解决方法：

如果向量是 2D，您始终可以将它们打包为复数。
您可以只对结果建立索引。例如 v = f(x,y) 并使用 v(1) 和 v(2)
使用 deal< /代码>如下：
f=@(x,y) deal(-y, x) [a,b] = f(1,2) 返回：a=-2 和 b=1

在我看来，第二个选项是最干净的（或者您可以只声明一个 function 而不是使用内联函数。MATLAB现在支持函数内的函数，类似于 python）。

It does seem strange that inline functions cannot return more than one output. Several workarounds are possible:

If the vectors are 2D, you can always pack them as a complex number.
You can just index the result. E.g. v = f(x,y) and use v(1) and v(2)
Use deal as follows:
```
f=@(x,y) deal(-y, x)
[a,b] = f(1,2)
```
Returns: a=-2 and b=1

The 2nd option is the cleanest, in my opinion (Or you can just declare a function instead of using an inline function. MATLAB now supports functions within functions, similar to python).

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