how diff command works?

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vrutang 2013-6-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/79496-how-diff-command-works

Respected Sir, I have following data.

-2.94000542962793  -0.000891548563348562
-3.08711094258045  -0.000486202607067662
-3.16733437274661  0.000246165485256576
-3.12671706767928  0.00102294399111758
-2.95793130914487  0.000749214351318326
-2.83431094117735  0.00309004687573728
-2.32445320668070  0.00366899717584366
-1.71906867266650  0.00439248318546055
-0.994308947065506  0.00491652606519422
-0.183082146308459  0.00463391434268762
0.581513720234998  0.00441428466119678
1.30987068933247  0.00436179962701698
2.02956762779027  0.00343887048751685
2.59698125823055  0.00324265720589084
3.13201969720254  0.00324830944034097
3.66799075485880  0.00297215741434881
4.15839672822635  0.00182233143477911
4.45908141496490  0.000300265443564988
4.50862521315313  -1.10444356313665e-07
4.50860698983434  -1.10444356313665e-07

left most is my original data and right most is diff of that data. Can you help me to know how it will give me this result?

Thaaks.

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Andrew Newell 2013-6-19

What do you mean when you say that the right column is the diff of the left? The difference between the first two numbers is -0.1471, not -0.00089.

Jan 2013-6-19

Showing only two vectors does not explain the relation between them. Please show us (by editing the original message), how you have created the right column. Otherwise there is an infinite number of possible way to obtain one dataset from another one.

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Answer 1

Roger Stafford 2013-6-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/79496-how-diff-command-works#answer_89242

编辑：Roger Stafford 2013-6-19

You have clearly created the rightmost column by taking the 'diff' of the left column and dividing by 165, and then duplicating the last element. Can you tell us why you have done this? Also I don't understand what it is you are asking. If you are attempting to approximate a derivative, you can get better results with matlab's 'gradient' function.