How to generate second order best fit polynomial curve using MATLAB

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Dan Mathotaarchchi
Dan Mathotaarchchi 2017-5-30
评论： Dan Mathotaarchchi 2017-6-1
Hi all can anybody tell me how to generate above equation for this x and y data using MATLAB ? x,y coordinates are 100,200 200,500 300,900 400,1400 500,2000

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Musa
Musa 2017-5-30
编辑：Musa 2017-5-30
Dan,
You can do this using poly2
x=[100 200 300 400 500]';
y=[200 500 900 1400 2000]';
ft = fittype( 'poly2' ); % Set up fittype and options.
[fitresult, gof] = fit( x, y, ft ); % Fit model to data.
f=@(x) fitresult.p1*x.^2+fitresult.p2*x+fitresult.p3;
plot(x,y,x,f(x),'o')
  1 个评论
Dan Mathotaarchchi
Dan Mathotaarchchi 2017-6-1
thank you Musa, now i got following problem to be solved. but i couldnt find a source that enables me to coding. do you know how to solve system of equations with successive substitution by coding with MATLAB. this is the problem,
the successive substitution method is expected to applied. .7 equations and 7 unknowns which are p,Q,m,T,z,b,W and W is the final answer , m=5 can be taken as initial guess. W Vs no of iterations to be graphed ?
p = -3.86*m^2+42.45*m+344.00 ;Q = 5*p^2+4.45*p+4.00 ; m = 2*p^2+4.5*p+14.00 + 5*p^2*T^2+4.45*pT+4.00T ; z=T^2(3*p^2+2.45*p+4.00)+ 3*p^2*T^2+1.45*pT+2.00T ; Q=3m(b-T) ; 800=4m(T-b) ; W=z-Q ;

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