Save value from overwriting in while loop

end

In this while loop I want to save u(end) and u1(end) in a vector but when i Try to do it it becomes problematic. Firslty I know how to do it if it only would been one variable (u), but in m case it is u1 too. For every iteration u1 and u ( last element of those ) gets overwritten so I dont know how to save u and u1 ( last elements) in a vector.

[Ameer Hamza]

Mohammed Hassan, This forum is for public benefit. Deleting the code in question makes the question meaningless for anyone else. I am restoring the code so that anyone else coming to this form can have a better idea about the original question.

[Ameer Hamza]

Text of original Question:

hI
En=50
While d >tollerance
[g u] = main(En,k)
En=En*3;
[g u1] = main(En,k)
d=abs((u(En/3)+1)-u1(En+1));
end

In this while loop I want to save u(end) and u1(end) in a vector but when i Try to do it it becomes problematic. Firslty I know how to do it if it only would been one variable (u), but in m case it is u1 too. For every iteration u1 and u ( last element of those ) gets overwritten so I dont know how to save u and u1 ( last elements) in a vector.

Answer 1

[Ameer Hamza]

The most simplest way is to let the array grow dynamically

En=50
u = [];
u1 = [];
while d >tollerance
[g u(end+1)] = main(En,k)
En=En*3;
[g u1(end+1)] = main(En,k)
d=abs((u(En/3)+1)-u1(En+1));
end

For an efficient solution. See this FEX submission from John: https://www.mathworks.com/matlabcentral/answers/510713-is-it-possible-to-store-the-intermediate-values-of-fmincon

[mohamed hassan]

Also, I want the values to be in the same vector where the first value will be u and the second u1 and the third u and the fourth u1 so and so on.

[Ameer Hamza]

Are the outputs of main(En,k) scalar or a vector?

[mohamed hassan]

oh when the mainfiles runs I get a vector with many values of g and the same for u. But I am only intrested in the last value of u so I want to store it in a new vector where I have the last element for u and u1.

[Ameer Hamza]

Ok, you can do something like this.

En=50
u = [];
while d >tollerance
[g temp] = main(En,k)
u(end+1) = temp(end);
En=En*3;
[g temp] = main(En,k)
u(end+1) = temp(end);
d=abs((u(En/3)+1)-u1(En+1));
end

Note that it create vector u such that odd elements u(1), u(3), u(5) contain value from first main() and even elelemts contain values from second main()

[mohamed hassan]

So you ignored u1 ?

[mohamed hassan]

I think something is mising from your ? you just replicated the lines ? and do I need to define temp before ? or do I need to disp u in the end ?

[Ameer Hamza]

You mentioned before "Also, I want the values to be in the same vector where the first value will be u and the second u1 and the third u and the fourth u1 so and so on". So my code create one vector u and save all elements in it.

"do I need to define temp before". No. temp is output variable. You don't need to define it before.

"do I need to disp u in the end". yes, If you want to see the value of u in the command window, then use disp(u)

[Ameer Hamza]

Oh! I missed that u1. Are you trying to subtract the value of u and u1 (from your code) in each loop. If yes, then try this

En=50
u = [];
while d >tollerance
[g temp1] = main(En,k)
u(end+1) = temp1(end);
En=En*3;
[g temp2] = main(En,k)
u(end+1) = temp2(end);
d=abs(temp1-temp2);
end

[mohamed hassan]

and in you latest code, ou save the vector from main as temp 1 and store it in the last element in u ? is that correct ?

[Ameer Hamza]

I missed the to assign last elements of temp1 and temp2. Now try the updated code in my last comment. I think it should do what you want.

[mohamed hassan]

Thanks It worked! but I dont actually understand the line u(end+1) = temp1(end);. could you explain it ?

[Ameer Hamza]

'temp1(end)' means that the last element of the vector temp1. Since you mentioned that main() returns a vector, and you want to keep the last value of that vector. The 'temp1(end)' keeps that last value.

u(end+1) tells the MATLAB to extend the array 'u' and add the new element to the extended location. This makes sure that the last value is not overwritten.

[mohamed hassan]

Thank you , I just wondering if it's possible to make it more adaptive ? more efficient, because I use the same kinda code twice in the loop?