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 :(

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

[Nikolas Katsantonis]

I need an answer ASAP please!

[Nikolas Katsantonis]

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]

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.

Answer 1

[Geoff Hayes]

@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).

[Nikolas Katsantonis]

I dont know how much I should thank you!!! Ive spent 8 hours on that :(

[Nikolas Katsantonis]

@Geoff Hayes One quick remark, My code now looks like that, it returns the A values however not the B, any suggestions?

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

function [A, B]= test(n,Coordinates)

A(n)= Coordinates*3;

B(n)= A(n)*Coordinates*6;

end

[Geoff Hayes]

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

Coordinates is passed in as an input parameter but is reset with 3+n. Is this intentional? Also, since test doesn't return arrays, then just do

myData1(n)= aValue;

[Nikolas Katsantonis]

@Geoff Hayes Yes, it now works perfectly, thank you a lot!!