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Hello everyone, anyone knows how to approximate a data with polynomial of degree 8 using least square method?

조회 수: 1(최근 30일)
Mohammad Shafi Nikzada
Mohammad Shafi Nikzada 2021년 6월 24일
답변: Walter Roberson 2021년 6월 25일
Polynomial degree is 8 and it should be approximated piecewise.
  • y = a0t0 + a1t1 + a2t2 + + antn ………………………….. (1)
Data description:
The first column is Time(GPS format) unit is seconds.
Second column is y values, so I have to find the coefficients (a0, a1...). And this should be done peicewise (9 points), then iterate this method till the end of the data.
Data is attached.
  댓글 수: 5
Matt J
Matt J 2021년 6월 25일
Your data looks very sinuisoidal. Are you sure you couldn't convince your assistant prof. just to fit a sinusoid?

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답변(2개)

Walter Roberson
Walter Roberson 2021년 6월 25일
Loop, moving one point at a time. At each location use polyfit on 9 points to create coefficients. polyder() https://www.mathworks.com/help/matlab/ref/polyder.html and evaluate to get velocity. polyder() again and evaluate to get acceleration.
Then move one point further on.

David Hill
David Hill 2021년 6월 25일
편집: David Hill 2021년 6월 25일
Use polyfit, place the x and y columns of your data into the function.
p=polyfit(x,y,8);%you will need to convert time using datenum and likely normalize

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