array manipulation in loop through a sequence

Question

RAJ 2019-9-2

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/478601-array-manipulation-in-loop-through-a-sequence

评论： RAJ 2019-9-5

采纳的回答： Andrei Bobrov

在 MATLAB Online 中打开

Dear programmers

I have defined an array of 4 values with 1 in all the rows initially as : tissue = [1 1 1 1]

After 1st iteration, I want to replace '1' at 4th position by '2' as: [1 1 1 2].

After 2nd iteration, '2' wil be shifted to 3rd position and new value '3' will take the 4th position as: [1 1 2 3 ] .

After 3rd iteration, '2' wil be shifted to 2nd position ,'3' wil be shifted to 3rd position and new value '4' will take the 4th position as: [1 2 3 4].

After 4th iteration, '2' wil be shifted to 1st position ,'3' wil be shifted to 2nd position, '4' wil be shifted to 3rd position and new value '5' will take the 4th position as: [2 3 4 5].

In the below code even if I am being asked the iteration number but I am getting the results only for the i=4. Where am I doing the error ? Please help!

 E = zeros(1,4);
for i=1:4
E(i) = 1
end
prompt = 'What is the iteration number? ';
i = input(prompt)
for i=1:4
E(5-i)= 2
for i=2:4
E(6-i)= 3
for i=3:4
E(7-i)= 4
for i=4
E(4)=5
end
end
end
end

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Walter Roberson 2019-9-2

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i = input(prompt)

assigns a particular value to i according to the user's input

for i=1:4

then overwrites i with the value 1, then 2, then 3, then 4.

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Answer 1

Andrei Bobrov 2019-9-2

1
链接

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https://ww2.mathworks.cn/matlabcentral/answers/478601-array-manipulation-in-loop-through-a-sequence#answer_390113

在 MATLAB Online 中打开

E = ones(4);
n = size(E,1);
for ii = 1:n
    E(ii,n-ii+1:n) = E(ii - 1 + (ii == 1),n-ii+1:n) + 1
end

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Andrei Bobrov 2019-9-5

在 MATLAB Online 中打开

E = ones(1,4);
A = zeros(4);
for ii = 1:4
    E(end - ii + 1 : end) = E(end - ii + 1 : end) + 1
    A(ii,:) = E;
end

RAJ 2019-9-5

demo text for E for smoothing.txt

Thanks Mr. Andrei your kind help and sorry for bothering you again .

It is almost done. But in the problem if the values are not incremented by 1 as in this case 2,3,4 and 5 but rather the values are random say 20,300.5,60 and 1.5. In that case the code is not working because in actual problem that I am working on, the values of E at 4th position can be anything and those will be read from a text file(in which the first column will be for an element and 2nd column is the E value that will take the position of E4 everytime and replace the previously positioned E4 to E3 i.e push one position ahead).

N.B: I am attaching the text file herewith. In the text file the 1st column is the finite element number and the 2nd column corresponds to the respective E that will take the place of E4. Such text files will be read in every iteration of the main program. I have tried to make a separate function by do loop to retrieve those E values row wise but that is not working.

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