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How to curve fit an equation with sigma function

조회 수: 6(최근 30일)
Gaurav Nanajkar
Gaurav Nanajkar 2019년 7월 25일
편집: Matt J 2019년 7월 29일
Dear all,
I would like to get coefficient C0, C1....CN from the below equation,
function.JPG
I have enclosed herewith an excel having x and y co-ordinates.
Can anybody please let me know how to write this equation in 'custom equation' option in curve fitting tool or is there any other way to do it?

답변(2개)

Alex Sha
Alex Sha 2019년 7월 27일
Hi, where are the values of Z?
  댓글 수: 1
Gaurav Nanajkar
Gaurav Nanajkar 2019년 7월 27일
Hi Alex, I saw the details of the equation and according to that this equation is for 'rotationally symmetric polynomial'. As I am using it for 2D curve, in my case Z value will be 0

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Catalytic
Catalytic 2019년 7월 27일
C = polyfit( sqrt( x.^2+y.^2) , Z, N)
  댓글 수: 4
Matt J
Matt J 2019년 7월 29일
As you mentioned as its a higher order polynomial I will not use polyfit due to higher perecentage error.
No, that is not what I said. What I said was "It's not that polyfit is better or worse at fitting high order polynomials. It's just that high order polynomials are typically a bad thing...".
Stop using high order polynomials. Use splines instead.

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