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Asked by Light on 26 May 2013

Hello!! I need help!! For Iteration

Here is my first iteration:

```S12t=6+2*1i;
S01t=10+5*1i;
U0=110;
U1=110;
U2=110;
R12 = 16.2+24*1i;
U0i=115;
R01= 15.75+31.2*1i;
dx01=106.125;
dx12=81;
U20=10;
e=0.01;
```
```dQ12=dx12*U2.^2*10.^-6;
S12i=S12t-complex(0,dQ12);
DS12 =((real(S12i).^2+imag(S12i).^2)/U2.^2)*R12;
S12ii=DS12+S12i;
S12e=S12ii-complex(0,dQ12);
```
```S01i=S12e+S01t;
dQ01=dx01*U1.^2*10.^-6;
S01ii=S01i-complex(0,dQ01);
DS01=((real(S01ii).^2+imag(S01ii).^2)/U1.^2)*R01;
dQ01i=dx01*U0i.^2*10.^-6;
S01ii2=S01ii+DS01;
S01iii=S01ii2-complex(0,dQ01i);
```
```dU01i=(real(S01ii2)*real(R01)+imag(S01ii2)*imag(R01))./U0i;
dU01ii=(real(S01ii2)*imag(R01)-imag(S01ii2)*real(R01))./U0i;
U1=sqrt((U0i-dU01i).^2+dU01ii.^2);
```
```dU12i=(real(S12ii)*real(R12)+imag(S12ii)*imag(R12))./U1;
dU12ii=(real(S12ii)*imag(R12)-imag(S12ii)*real(R12))./U1;
U2=sqrt((U1-dU12i).^2+dU12ii.^2);
```

And i want it continue to next iteration.

continue it if U0-(max of U1 U2)>e

U1 U2 will be changed last 2 value in next iteration

end it if U0-(max of U1 U2)<e

How can i put the if continue (while, return, end )

I can't understand I tried so many times, but still error message "usage might invalid Matlab syntax" appeared.

Just help me tell where can i put that statements If, while, continue in Long Function. Please help me!!

Thank You!!

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Answer by Walter Roberson on 26 May 2013

I have not studied the code thoroughly but it appears to me that you do not assign new values to any variables you used previously. Unless at least one input variable gets a new value, then when you iterate the results would have to come out exactly the same and you would iterate forever. Something needs to change inside the loop before you can hope to have your iteration terminate.

Your general code structure will look something like this:

```Initialize your variables
```
```while true     %"true" is literal here, not an example variable name
```
```    Do some calculation
break;    %"break" is literal, a MATLAB command
end```
```    %you only get here if you did not break out, so if the termination
%condition did not hold```
`   end   %of while loop. If the termination condition did not hold, loop back`

Walter Roberson on 26 May 2013

You start out with U1 and U2 being the same, so their difference is 0, which is less than e, so your loop would not run if you use that "while".

```S12t=6+2*1i;
S01t=10+5*1i;
U0=110;
U1=110;
U2=110;
R12 = 16.2+24*1i;
U0i=115;
R01= 15.75+31.2*1i;
dx01=106.125;
dx12=81;
U20=10;
e=0.01;
```
```iteration_number = 0;
```
```while true
```
```    iteration_number = iteration_number + 1;
fprintf('Starting iteration #%d\n', iteration_number);```
```    dQ12=dx12*U2.^2*10.^-6;
S12i=S12t-complex(0,dQ12);
DS12 =((real(S12i).^2+imag(S12i).^2)/U2.^2)*R12;
S12ii=DS12+S12i;
S12e=S12ii-complex(0,dQ12);```
`    .... and so on ...`
```    if U0-max(U1,U2) <= e
break;
end```
```end
```
Light on 26 May 2013

Thank you very much!! Almost done.

But it stopped at iteration 1 unless prove that U0-U2 <= e.

It must reach iteration 3

How can i give iteration number?

And can i model it in Simulink by whileloop block?

It is embarrassing asking so many thing Sorry :-)

Walter Roberson on 26 May 2013

No, the code will stop because it finds that U0-U2 <= e . Remember what I wrote earlier about you starting out U1 and U2 with the same value. Any algorithm that tries to iterate to find something between the two of them is going to stop because they are the same already.

I do not know what you mean about "How can I give iteration number" ?