# How to get original values from cumulative sum values?

조회 수: 6(최근 30일)
Niraj Bal Tamang 2022년 6월 19일
답변: Stephen23 2022년 6월 19일
I have a list of cumulative sum values. I want to obtain another list with the values that generated the cumulative sum vaues. Something like a reverse cumulative sum process. I tried (X2-X1) formula for each consecutive value but couldn't get the exact values. Can someone please help me to reverse the cumulative sum values to original values.
Thank you

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### 채택된 답변

Stephen23 2022년 6월 19일
X = rand(1,9)
X = 1×9
0.8615 0.8710 0.7907 0.5073 0.3673 0.4523 0.4018 0.2258 0.1596
Y = cumsum(X)
Y = 1×9
0.8615 1.7326 2.5233 3.0306 3.3979 3.8502 4.2520 4.4778 4.6374
Z = [Y(1),diff(Y)]
Z = 1×9
0.8615 0.8710 0.7907 0.5073 0.3673 0.4523 0.4018 0.2258 0.1596
max(X-Z) % alomsot zero
ans = 4.4409e-16
Because of the accumulated floating point error getting exactly the same values is not expected.

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