how to use function handles

3 次查看（过去 30 天）

显示更早的评论

G A 2021-8-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1442829-how-to-use-function-handles

评论： G A 2021-8-31

采纳的回答： Yongjian Feng

在 MATLAB Online 中打开

Instead of the following, I want to use function handles and move if-statments out of the loop:

for n=1:10
    if a==0
        A = function2(n,a,b);
    else
        A = function1(n,a,b,c,d);
    end
end
function A = function1(n,a,b,c,d)
A = n+a+b+c+d; % here it can be any expression
end
function A = function2(n,a,b)
A = n*a*b; % here it can be any expression
end

moving if-statement outside of the loop and using handles:

if a==0
    func = @function2;
else
    func = @function1;
end

and then I can solve my problem in two ways as

for n=1:10
    A = func(n,a,b,c,d);   
end
    
function A = function1(n,a,b,c,d)
A = n+a+b+c+d;
end
function A = function2(n,a,b,~,~)
A = n*a*b;
end

or as

for n=1:10
    A = func(n,a,b,c,d)   
end
    
function A = function1(n,a,varargin)
b = varargin{1};
c = varargin{2};
d = varargin{3};
A = n+a+b+c+d;
end
function A = function2(n,a,varargin)
b = varargin{1};
A = n*a*b;
end

Is there any more elegant way to do this?

采纳的回答

Yongjian Feng 2021-8-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1442829-how-to-use-function-handles#answer_776524

在 MATLAB Online 中打开

You don't need varargin

function A = function1(n,a,b, c, d)
A = n+a+b+c+d;
end
function A = function2(n,a,b, ~, ~)
A = n*a*b;
end

"what is the main difficulty to make (or reason not to make) it possible in the Editor to higlight structure name with its field throughout a function like it occurs with simple variables when you click on it or select it?"

You have to consider that variables in MATLAB are dynamically typed. In general it is difficult to determine the type of a variable until runtime (e.g. changes to function scoping, variables created dynamically, inputs are not typed, etc.)

G A 2021-8-31

Thanks! - and I will accept this answer together with comments.

请先登录，再进行评论。

更多回答（1 个）

the cyclist 2021-8-29

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1442829-how-to-use-function-handles#answer_776529

在 MATLAB Online 中打开

I think the basic idea you need is

f1 = @(x) x;
f2 = @(x) x.^2;
f = @(a,x) (a~=0)*f1(x) + (a==0)*f2(x);
f(0,2)
ans = 4
f(1,2)
ans = 2

4 个评论
显示 2更早的评论隐藏 2更早的评论

G A 2021-8-29

编辑：G A 2021-8-29

Also, it is time consuming if two functions are executed instead of one. Better to put if-statement into a loop. I have half of answer to my question in my comment above: 0*inf = NaN, 0*A = 0, so to give the answer 0 or NaN, Matlab must execute f2 before multipliing its return by 0.