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

2 views (last 30 days)
benghenia aek on 26 Nov 2021
Answered: Image Analyst on 27 Nov 2021
ho to find index at which the 50% of the sum vector is included?
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
Star Strider on 27 Nov 2021

Star Strider on 26 Nov 2021
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
.
Steven Lord on 26 Nov 2021
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

Image Analyst on 27 Nov 2021
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.)