ho to find index at which the 50% of the sum vector is included?

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benghenia aek 2021-11-26

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回答： Image Analyst 2021-11-27

a=[3 5 7 3 5 8 9 3 1 41 6];

sum(a)=91

50% of sum signal =45.5

indice which is approximately equal to of sum of 50% of sum signal a is 9

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Star Strider 2021-11-27

See also: how to find index of 50% of sum of signal?

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Answer 1

Star Strider 2021-11-26

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A least-squared-difference approach works —

a=[3 5 7 3 5 8 9 3 1 41 6];
suma = cumsum(a);
suma50 = suma(end)/2;
[minv,idxv] = min((suma50-suma).^2)
minv = 2.2500
idxv = 9

.

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Star Strider 2021-11-26

My pleasure!

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Steven Lord 2021-11-26

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If you want the first index that's past the halfway point:

a=[3 5 7 3 5 8 9 3 1 41 6];
suma = cumsum(a)
suma = 1×11
     3     8    15    18    23    31    40    43    44    85    91
suma50 = suma(end)/2
suma50 = 45.5000
[~, location] = find(suma > suma50, 1, 'first')
location = 10
suma([location-1 location])
ans = 1×2
    44    85

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Answer 2

Image Analyst 2021-11-27

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https://ww2.mathworks.cn/matlabcentral/answers/1596904-ho-to-find-index-at-which-the-50-of-the-sum-vector-is-included#answer_841374

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Isn't this a duplicate?

If it's not your homework, you can use my solution:

a = [3 5 7 3 5 8 9 3 1 41 6];
s = sum(a)
s = 91
c = cumsum(a)
c = 1×11
     3     8    15    18    23    31    40    43    44    85    91
[minDiff, index] = min(abs(c - s/2))
minDiff = 1.5000
index = 9

(If it is your homework, tag it as homework and find a different way. Don't turn in any of our solutions as your own or you may get caught for cheating.)