I want to use a for loop inside a function, where the for loop contains a subfuction. Each loop must store the variable value and make a matrix of all values, but I get 0s :(

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Nikolas Katsantonis 2022-6-17

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https://ww2.mathworks.cn/matlabcentral/answers/1742670-i-want-to-use-a-for-loop-inside-a-function-where-the-for-loop-contains-a-subfuction-each-loop-mus

评论： Nikolas Katsantonis 2022-6-18

function [a] = Main(Coordinates)
    a=5;
    for n=1:a
        Coordinates=3+n;
        a= test(n,Coordinates)
    end
end
function [A, B]= test(n,Coordinates)
    A(n)= Coordinates*3;
    B(n)= A(n)*Coordinates*6;
end

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Nikolas Katsantonis 2022-6-17

Bsicly the matrix is created however the older values are saved as 0s and only the last value of the loop is saved

Geoff Hayes 2022-6-17

在 MATLAB Online 中打开

That makes sense, right? Look at this code

function [A, B]= test(n,Coordinates)
    A(n)= Coordinates*3;
    B(n)= A(n)*Coordinates*6;
end

You are creating a new A and B whenever the test function is called. These new variables/arrays won't have the history from previous calls to this function. So you are always returning arrays of zeros except for the nth value which is set in this function call.

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Answer 1

Geoff Hayes 2022-6-17

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https://ww2.mathworks.cn/matlabcentral/answers/1742670-i-want-to-use-a-for-loop-inside-a-function-where-the-for-loop-contains-a-subfuction-each-loop-mus#answer_987795

在 MATLAB Online 中打开

@Nikolas Katsantonis - you are using a as an integer and as a result from test

    a=5;
    for n=1:a                  %<--- a as integer
        Coordinates=3+n;
        a= test(n,Coordinates) %<--- a as result
    end

test should be returning two values and not arrays (you will need to correct this code), and so you would do something like

    a=5;
    for n=1:a
        Coordinates=3+n;
        [aValue, bValue] = test(n,Coordinates);
    end

then store aValue into an array so that you don't overwrite it on each iteration of the loop

    a=5;
    myData = zeros(a,1);
    for n=1:a
        Coordinates=3+n;
        [aValue, bValue] = test(n,Coordinates);
        myData(n) = aValue;
    end

then return myData in the signature of your function (not a).

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Geoff Hayes 2022-6-17

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You could try changing this code to

function [A, B]= test(n,Coordinates)
A = Coordinates*3;
B = A*Coordinates*6;
end

though the n can be removed since it is no longer relevant. It isn't clear to me why b isn't being set...it does for me when I try it.

A couple more things from

function [myData1,aValue,bValue,n] = Untitleddd(Coordinates)
  a=5;
   myData1 = zeros(a,1);% Added
    for n=1:a
        Coordinates=3+n;
        [aValue, bValue] = test(n,Coordinates);
        myData1(n)= aValue(n);%Added
         
    end
end