problem in calculating mean from the required element of matrix??

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NAVNEET NAYAN 2017-5-5

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https://ww2.mathworks.cn/matlabcentral/answers/338837-problem-in-calculating-mean-from-the-required-element-of-matrix

编辑： KL 2017-5-5

I have a matrix mat6 of dimension 1-by-210. j =210. I am applying a threshold condition on mat6 and then i need to calculate the mean of next twenty elements . I want that the mean should be calculated from that first element of mat6 at which threshold condition was met at first time. But it is calculating mean from that last element of mat6 at which the threshold condition was met.

for k  = 1:j-20
if mat6(k)>0.5
    w=k+20;
   mea = sum(mat6(1,k:w))/20;
end
 end

can anyone please sort out this problem ??

Thanks

Navneet Nayan

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Jan 2017-5-5

k:k+20 are 21 elements, not 20.

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采纳的回答

KL 2017-5-5

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https://ww2.mathworks.cn/matlabcentral/answers/338837-problem-in-calculating-mean-from-the-required-element-of-matrix#answer_265748

编辑：KL 2017-5-5

在 MATLAB Online 中打开

k = 1;
while k <j-20
    if mat6(k)>0.5
        mea = mean(mat6(1,k:k+19))
        k=k+20;
    else
        k = k+1;
    end
end

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NAVNEET NAYAN 2017-5-5

thanks KL... It worked....

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更多回答（1 个）

Jan 2017-5-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/338837-problem-in-calculating-mean-from-the-required-element-of-matrix#answer_265752

编辑：Jan 2017-5-5

在 MATLAB Online 中打开

index = find(mat6 > 0.5, 1);  % Find 1 index only
mea   = mean(mat6(index:index+19));

Consider that index+19 might exceed the data size. Handle this situation e.g. by an error, e.g.:

index = find(mat6 > 0.5, 1);
if index + 19 > size(mat6, 2)
  error('Index out of range in mat6');
end

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NAVNEET NAYAN 2017-5-5

tell me one thing Jan, if i want to use the subsequent indices for eg. i want to use the second or 3rd index, how can I proceed??

KL 2017-5-5

编辑：KL 2017-5-5

在 MATLAB Online 中打开

index = find(mat6 > 0.5);
%this finds all the indices and then you could follow Andrei's command. (with the error check by Jan)
mea  = mean( mat6( bsxfun(@plus,index(:)',(0:19)')) );

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