For loop the last end first values problem

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Erkan 2021-8-31

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1443779-for-loop-the-last-end-first-values-problem

评论： Erkan 2021-9-3

Hi everybody, i have problem for loop. problem is that i dont take the last value of vector in the second loop to the first value of vector in the firts loop, below program code;

W=zeros(1,51);

A(1)=0;

for x=1:length(W)

for y=1:50

A(y+1)=A(y)+...........

end

W(x)=A(end); (when i make in this way, the all value of vector W is being the same)

end

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DGM 2021-9-1

在 MATLAB Online 中打开

I haven't been at the computer much today.

Looking at it, Se2 is being filled with NaN. If you put the following inside the innermost loop (at the end):

if isnan(Ne(i+1))
    [j x i] % show the loop indices
	return;
end

execution will stop once things start turning NaN. You can see that Se is NaN because p3,p4 are NaN (and p1 and p2 are approaching absurdly large values). These are NaN because Ne is NaN. Ne is NaN because the m# variables are NaN. The m# variables are NaN because the arguments to fNe() are approaching Inf. The operations within fNe() result in two of the terms being Inf. Inf-Inf is NaN. If you plot any of the partially populated vectors, you should be able to look at a subset of the vector and see the rapid growth.

I don't have a ready solution for this. I don't really have my head wrapped around what the code is doing mathematically. You'll have to figure out what this observation means in that context. You can make use of breakpoints or simple tests like that shown above to try to supervise the process and further troubleshoot. If possible, it may help to break the problem into parts to simplify testing.

Erkan 2021-9-1

编辑：Erkan 2021-9-1

myscript.m

Hello DGM and Mathieu

Firstly, thanks you for interested in my problem. Actually the iteration numbers of the 2nd and 3rd loops are more high, 2nd loop: 1001 and 3rd loop:1000. i intently given small values to take short time while working your. yes, in the small iteration values heppen the NaN states but not more high iteration values. i edited my program and added.

Erkan 2021-9-3

Hi again, i solved the problem in my program. Error is due to no any a connect between the 2nd and 3rd looop. i taken RN variable in program into the 2nd loop, problem is solved. i wanted to share so that for anyone become useful.

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回答（1 个）

Mathieu NOE 2021-8-31

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1443779-for-loop-the-last-end-first-values-problem#answer_777629

在 MATLAB Online 中打开

hello

your code works - depends what you do in the first loop. here with rand to create different outputs for A(end)

you could have preallocated memory for A as well (as for W)

My results for W :

W =

Columns 1 through 5

25.9275 24.6355 28.5185 24.8521 24.2186

Columns 6 through 10

28.4241 24.2731 27.0010 26.0431 22.7694

Columns 11 through 15

24.4161 25.4517 25.1269 26.4411 25.9014

Columns 16 through 20

29.2451 25.3311 25.1996 24.2821 25.5079

Columns 21 through 25

26.7850 25.5720 24.6583 28.1824 23.9135

Columns 26 through 30

26.2461 24.0711 27.3557 25.0476 25.6504

Columns 31 through 35

24.8361 23.7875 26.3622 24.0471 26.9280

Columns 36 through 40

23.7483 21.7386 24.6370 25.7321 24.5716

Columns 41 through 45

26.3787 23.5214 26.7891 26.3458 27.8958

Columns 46 through 50

24.5838 24.4152 21.9655 26.6178 21.9926

Column 51

27.9023

Code :

clc
clearvars
W=zeros(1,51);
A=zeros(1,51);
for x=1:length(W)
    for y=1:50
     A(y+1)=A(y)+rand(1);
    end
W(x)=A(end);               % (when i make in this way, the all value of vector W is being the same)
end