How to return a vector output when a vector input is given to a function_handle representing a constant function?
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I want to define a function handle that represents the constant function
, pass an n-length vector input, and get out an n-length vector whose values are c. But there's a catch. My code is like:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1689127/image.png)
% Usual Case
syms x; syms t;
u = symfun(x^2,x);
u_x = diff(u,x);
u_x = matlabFunction(u_x);
u_x([0 1 2])
ans = [0 2 4];
So, I input a vector, and I get back a vector, which I would consider the "expected" behavior. But it might happen that the input function happens to have a constant derivative, like
% Exceptional Case
syms x; syms t;
u = symfun(x,x);
u_x = diff(u,x);
u_x = matlabFunction(u_x);
u_x([0 1 2])
ans = 1
Now, I put in a vector and suddenly MATLAB returns a scalar.
So if I only ever had the exceptional case, I would just do something like u_x(0) * ones(1,3) to get my desired vector of constants. But actually, I almost never have the exceptional case; most of the time the input function does not have a constant derivative, and so inputing a vector into the differentiated function returns a vector already.
What I want is for MATLAB to do what I would consider the obvious thing: If I input a vector, I get back a vector, even if the function_handle represents a constant function...how do I do?
Thanks!
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回答 (1 件)
Torsten
2024 年 5 月 7 日
編集済み: Torsten
2024 年 5 月 7 日
This works in both cases:
% Usual Case
syms x; syms t;
u = symfun(x^2,x);
u_x = diff(u,x);
u_x = matlabFunction(u_x);
u_x = @(x)u_x(x).*ones(size(x));
u_x([0 1 2])
% Exceptional Case
syms x; syms t;
u = symfun(x,x);
u_x = diff(u,x);
u_x = matlabFunction(u_x);
u_x = @(x)u_x(x).*ones(size(x));
u_x([0 1 2])
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