two columns of numbers with the second one sum on steps according to repeated numbers on first column

Question

Georgios Tsiledakis 2023-3-31

0
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https://ww2.mathworks.cn/matlabcentral/answers/1938529-two-columns-of-numbers-with-the-second-one-sum-on-steps-according-to-repeated-numbers-on-first-colum

评论： Georgios Tsiledakis 2023-3-31

采纳的回答： Dyuman Joshi

Dear experts,

I have an data file with 2 columns, data.txt --> input having thousands of lines...

In the 1st column, an integer number is increasing being repeated several times.

In the output I would like to have the sum of each next value added in the second column for each repeated number on 1st column.

input input output

---------------------

1 0.5 0.5 0.5

1 0.4 0.9 0.5 + 0.4

1 0.2 1.1 0.5 + 0.4 + 0.2

2 0.1 0.1 0.1

2 0.2 0.3 0.1 + 0.2

2 0.4 0.7 0.1 + 0.2 + 0.4

3 0.6 0.6 0.6

3 0.2 0.8 0.6 + 0.2

...................

I did something like:

load data.txt

C=(data(:,2));

[a,b] = unique(data(:,1));

[~,d] = unique(data(:,1),'last');

for i = 1 : size(a,1)

B1(i) = sum(C(b(i):d(i),1));

end

%disp(B1)

B = [B1' a]

But I got

B =

1.1000 1.0000

0.7000 2.0000

0.8000 3.0000

Any help please?

Best regards

Georgios

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Answer 1

Dyuman Joshi 2023-3-31

编辑：Dyuman Joshi 2023-3-31

在 MATLAB Online 中打开

For continuous repetition -

in1 = [1;1;1;2;2;2;3;3];
in2 = [0.5;0.4;0.2;0.1;0.2;0.4;0.6;0.2];
for k=2:numel(in1)
    if in1(k)==in1(k-1)
        in2(k)=in2(k)+in2(k-1);
    end
end
in2
in2 = 8×1
    0.5000
    0.9000
    1.1000
    0.1000
    0.3000
    0.7000
    0.6000
    0.8000