plot and fit surface

조회 수: 18 (최근 30일)
laura bagnale
laura bagnale 2021년 5월 25일
댓글: laura bagnale 2021년 6월 9일
Hello everyone,
I hope that someone can help me.
I'm trying to plot several points in the space and to fit them so I can get an mathematical formula like this topic https://de.mathworks.com/help/curvefit/polynomial.html#bt9ykh7 "Fit and Plot a Polynomial Surface"
I want to get a quadratic polynomial so I'm trying to use 'poly22' function. This is my code:
X = [0; 1; 1; -1; -1; 0.3]
Y = [0; 1 ; -1; -1; 1; 0.5]
Z = [0.9; 0.3; 0; 0.2; 0.6; 1]
plot3(X,Y,Z,'or')
z = Z;
fitsurface=fit([X,Y],z, 'poly22','Normalize','on')
plot(fitsurface, [X,Y],z)
I obtained this results:
Linear model Poly22:
fitsurface(x,y) = p00 + p10*x + p01*y + p20*x^2 + p11*x*y + p02*y^2
where x is normalized by mean 0.05 and std 0.9028
and where y is normalized by mean 0.08333 and std 0.9174
Coefficients:
p00 = 0.9097
p10 = -0.2332
p01 = 0.2645
p20 = -1.07
p11 = -0.02071
p02 = 0.5786
But I am not sure about them and the syntax.
Could you help me please?
Thank you a lot!
Laura

채택된 답변

Mahesh Taparia
Mahesh Taparia 2021년 6월 4일
Hi
The syntax and code which you have used is correct. The above code will fit a 2nd degree polynomial to the given data points and this is what you need.
  댓글 수: 17
Walter Roberson
Walter Roberson 2021년 6월 9일
When you have a minimization problem, analytic solutions are best unless they would take an undue amount of time.
(There are some minimization problems that can be approached probabilisticly to get a likely solution in a relatively short time, but proving that the answer is the best possible might take a long time. There is a famous mathematical problem involving one of the largest numbers ever invented, literally too large to write down in this universe... for a situation where it is suspected that the real minimum is 6. So sometimes it really does not pay to do a complete analysis. But in a situation like the function you have, you might as well go for the analysis and so be sure that you have the right solution.
laura bagnale
laura bagnale 2021년 6월 9일
I understand.
Thank you very much for the quick answers, the explanation and the support!
Kind Regards,
Laura

댓글을 달려면 로그인하십시오.

추가 답변 (0개)

카테고리

Help CenterFile Exchange에서 Matrices and Arrays에 대해 자세히 알아보기

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by