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How can we define a function with variables which are in the for loop and function is also under for loop?

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Surath Ghosh
Surath Ghosh 2020-9-11
评论： Surath Ghosh 2020-9-12
I want to define the function as
For i=1:100
fi(x0,x1, x2, ....xi)=x0^2+x1^2+.....xi^2
end
where for loop is on the functions(fi) as well as on the variables.
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Stephen23
Stephen23 2020-9-11
"but I have to write 1000 functions of 1000 variables. what should I do now??"
Use arrays and indexing, then you can solve your task efficiently using MATLAB.
Using 1000 different variables would not be a good use of MATLAB.

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回答（2 个）

KSSV
KSSV 2020-9-11
编辑：KSSV 2020-9-11
Read about anonymous function.
EXample:
f = @(x1,x2,x3) 2*x1.^3+3*x2.^2+x3 ;
x1 = rand(10,1) ; x2 = rand(10,1) ; x3 = rand(10,1) ;
val = f(x1,x2,x3)
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KSSV
KSSV 2020-9-11
You are not supposed to have like that...that case, you need to collect them into a matrix and do the below:
f = @(x1,x2,x3) x1.^2+x2.^2+x3.^2 ;
x1 = rand(10,1) ; x2 = rand(10,1) ; x3 = rand(10,1) ;
val = f(x1,x2,x3)
p = sum([x1 x2 x3].^2,2) ; % you need to do this
Steven Lord
Steven Lord 2020-9-11
I recommend not having your function accept 1000 separate input arguments. Write one general function.
f = @(x) sum(x.^2);
Now you can call it with however long a vector you want.
f(1:5)
f(1:10)
f(2:2:8)
If you're using a sufficiently recent release, you could even have f accept arrays.
g = @(x) sum(x.^2, 'all');
g(magic(3))

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Ameer Hamza
Ameer Hamza 2020-9-11
If you want to have a variable number of inputs, you can use varargin
f = @(varargin) sum([varargin{:}].^2);
Result
>> f(1,1,5)
ans =
27
>> f(1,1,5,22,32,34,1,2,3,4,5,1,2,3,45,32,23,10)
ans =
6438

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