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I have plotted x vs y and obtained a plot of points, now I'm trying to fit a curve to my data using a nonlinear polynomial of order 4, the coeficiants are unknown.

I aim to obtain the regression coefficient as well.

Any idea how it is possible to do this? what are the suitable matlab functions to plot the fitting curve and to obtain the regression coeficient?

I already tried polyfit, but is it correct? if yes then how to proceed?

KSSV
on 19 Nov 2018

Edited: KSSV
on 19 Nov 2018

Yes polyfit is the function you need.

x = linspace(0,4*pi,50);

y = sin(x);

% Use polyfit to fit a 4th-degree polynomial to the points.

p = polyfit(x,y,7);

% Evaluate the polynomial on a finer grid and plot the results.

x1 = linspace(0,4*pi);

y1 = polyval(p,x1);

figure

plot(x,y,'o')

hold on

plot(x1,y1)

hold off

In the above p has your coefficients. YOu can use poly2sym to see the polynomial obtained.

madhan ravi
on 19 Nov 2018

x = linspace(0,4*pi,50);

y = sin(x);

xx = linspace(x(1),x(end),1000);

yy = interp1(x,y,xx,'spline')

plot(x,y,'o',xx,yy)

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