Executing same function in different elements of an array

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Yanjika O 2020-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/527943-executing-same-function-in-different-elements-of-an-array

评论： Stephen23 2020-5-21

Hi,

I have wrote a function for small calculation. And I have an array 'A' which has over 25000 elements. I would like to refer certain ranges like A(2500:2800), A(5000:5300) and so on.., execute above mantioned function on them. Also, getting separate outputs from each range of A that I have selected. I have tried using array fun but I couldn`t make it work.

Please give your recommendations in this case.

Thank you

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Answer 1

Stephen23 2020-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/527943-executing-same-function-in-different-elements-of-an-array#answer_434643

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Try something like this:

B = [2500,5000,...]; % begin indices
E = [2800,5300,...]; % end indices
N = numel(B);
C = cell(1,N);
for k = 1:N
    V = A(B(k):E(k));
    ... do whatever with subvector V
    C{k} = ... output of your code
end

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Yanjika O 2020-5-21

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Thank you for answering.

Here is what I tried so far. What I want here is

(1) Get the range of A from 10 to 20, 30 to 40, 50 to 60, 70 to 80 and 90 to 100

(2) Run the code below defining V vector starting from idx=V<5... for every range that I have defined on 1st step

(3) And get the summary result of how many of the element was met with my condition above by disp(f)

I still couldn`t fiure it out. There might be some wrong usafe of sth. Please suggest more.

A=(1:1:100);
B=A([10, 30, 50, 70, 90]);
C=A([20, 40, 60, 80, 100]);
N=numel(C);
D=cell(1:N);
for k=1:N
    V=A(B(k):C(k));
    idx=V<5; 
    ii1=strfind([0 idx 0],[0 1]); 
    ii2=strfind([0 idx 0],[1 0])-1;
    ii=(ii2-ii1+1)>=5;
    out=arrayfun(@(x,y)s(x:y),ii1(ii),ii2(ii),'un',0); 
    n=cellfun(@numel,cell(out));
    for n=n(:,:)'
    fd=(n/30);
    f=sum(fd);
    disp(f)
    end 
end

Stephen23 2020-5-21

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Replace the definitions of B and C with

B = [10,30,50,70,90];
C = [20,40,60,80,100]);

These are supposed to be vectors of indices. You used them to extract elements of A before the loop, and then in the loop you used those extracted elements of A as indices into A... which is unlikely to be very useful.

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