How to find the index of array that reach to an specific value

Question

arash rad 2022-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/1880147-how-to-find-the-index-of-array-that-reach-to-an-specific-value

回答： Image Analyst 2022-12-17

Hi everyone I have an array like this :

Columns 1 through 9

0 0 2 4 4 5 5 5 5

Columns 10 through 18

5 4 5 5 2 3 6 5 5

Columns 19 through 27

4 4 2 10 3 6 4 5 5

Column 28

2

and I want to calculate when in this array sum of how many of this element reaches to 10 and we can see in index 5 it reaches 10 then A = 5*T

I use cumsum for it and it gives me answer in first step

but again I don't know how to calculate the continue I mean that I want to calculate when again after index 5 the sum of element reach to 10 .

can anyone help me with it

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Torsten 2022-12-17

I use cumsum for it and it gives me answer in first step

but again I don't know how to calculate the continue I mean that I want to calculate when again after index 5 the sum of element reach to 10

Then look up when cumsum reaches 20.

the cyclist 2022-12-17

@arash rad, suppose when you reach a value of at least 10, you actually get the value 14 (not exactly 10). Do you want to include that "extra" 4 as you sum toward 20, or start over from 0 for the next sum?

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Answer 1

Image Analyst 2022-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/1880147-how-to-find-the-index-of-array-that-reach-to-an-specific-value#answer_1130152

在 MATLAB Online 中打开

How about this:

v = randi(9, 1, 20)
v = 1×20
     8     5     5     4     2     3     7     5     5     5     6     2     6     6     3     7     1     8     3     9
c = cumsum(v)
c = 1×20
     8    13    18    22    24    27    34    39    44    49    55    57    63    69    72    79    80    88    91   100
thresholds = 10 : 10 : 10*length(c)
thresholds = 1×20
    10    20    30    40    50    60    70    80    90   100   110   120   130   140   150   160   170   180   190   200
for k = 1 : length(c)
    t = find(c >= thresholds(k), 1, 'first');
    if ~isempty(t)
        indexes(k) = t;
    end
end
% Show indexes
indexes
indexes = 1×10
     2     4     7     9    11    13    15    17    19    20
% Show cumulative sums at those indexes.
cumValues = c(indexes)
cumValues = 1×10
    13    22    34    44    55    63    72    80    91   100