MATLAB中的部分函数评估

问题描述

在MATLAB函数中是否存在绑定变量的惯用方法？看起来创建一个函数，绑定几个参数，然后将这个新函数传递给某种优化器（在我的例子中，是一个牛顿求解器）是相当普遍的。它看起来不像变量范围规则允许使用嵌套或内联函数的解决方案。我应该简单地创建一个班级吗？似乎MATLAB没有一流的函数对象，这是正确的吗？我的搜寻功夫即将到来。作为一个例子，假设我想找到f（c，x）= x ^ 3 + cx ^ 2 + 2x + 3对于各种值的根的参数c。我有一个牛顿方法求解器，它只接受一个变量的函数，而不是两个。所以我循环了c的各种值，然后将绑定函数传递给求解器。

  for c = 1：10 
G = F（C）; ％以某种方式绑定c 
 seed = 1.1的值; ％我猜测方程的根
 root = newton（g，seed）; ％计算实际根目录
结束
  

解决方案

您可以这样做：

  f = @（c，x）（@（x）（x ^ 3 + c * x ^ 2 + 2 * x + 3））; 
 
 for c = 1：10 
 g = f（c）; ％g是@（x）（x ^ 3 + c * x ^ 2 + 2 * x + 3）对于那个c 
 .... 
结束
  

关键是第一行：它是一个返回函数的函数。

Ie ，它返回 @（x）（x ^ 3 + c * x ^ 2 + 2 * x + 3），其值 c 绑定。

Is there an idiomatic way to bind variables in a MATLAB function? It seems like it would be fairly common to create a function, bind a few arguments, then pass the new function to an optimizer of some sort (in my case, a Newton solver). It doesn't look like the variable scoping rules permit a solution with nested or inline functions. Should I simply create a class? It doesn't seem like MATLAB has first-class function objects, is this correct? My search kung-fu is coming up short. Thanks!

As an example, suppose I want to find the roots of f(c,x)=x^3+cx^2+2x+3 for various values of the parameter c. I have a Newton's method solver which takes a function of one variable, not two. So I loop over various values of c, then pass the bound function to the solver.

for c=1:10
  g=f(c); % somehow bind value of c
  seed=1.1; % my guess for the root of the equation
  root=newton(g,seed); % compute the actual root
end

解决方案

You can do it like this:

f = @(c,x)( @(x)(x^3+c*x^2+2*x+3) );

for c=1:10
    g=f(c); % g is @(x)(x^3+c*x^2+2*x+3) for that c
    ....
end

The key is the first line: it's a function that returns a function.

I.e., it returns @(x)(x^3+c*x^2+2*x+3), with the value of c bound in.

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