How to plot the least square method?

RoBoTBoY

2021 4 24

0 个回答

8 次查看（30 天）

0 个投票

Kd_Kp.xlsx

Hello!

I have these measurements of an experiment where Kp and Kd are the coefficients of PD controller and model displays critical damping at these measurements.

I want to find the ideal curve with respect to least sqruare method.

How to do that?

I tried that but I don't know if is true.

plot(Kd,Kp,'go')
hold on
f = fit(Kd,Kp,'poly2');
plot(f,Kd,Kp,'b--')
xlim([0.2,1.3])
ylim([-2,22])
legend('Location','NorthWest');
hold off

3 个评论
显示 1更早的评论隐藏 1更早的评论

RoBoTBoY 2021-4-24

untitled.fig

How do I connect these points with a curve?

So this diagram I drew is wrong?

Star Strider 2021-4-24

在 MATLAB Online 中打开

'How do I connect these points with a curve?’

Whatever works, unless you have a mathematical model of the process that created them, and in that instance, use that mathematical model with a linear or nonlinear parameter estimation function. Then, using that function and the estimated parameters, calculate the fit and plot the line using those data.

One option is a spline fit —

Kd_Kp = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/595780/Kd_Kp.xlsx')

Kd_Kp = 4×2 table

Kp Kd __ ___ 1 0.3 5 0.6 10 0.8 20 1.2

Kd_v = linspace(min(Kd_Kp.Kd), max(Kd_Kp.Kd));

Kp_v = spline(Kd_Kp.Kd, Kd_Kp.Kp, Kd_v);

figure

scatter(Kd_Kp.Kd, Kd_Kp.Kp, 'filled')

hold on

plot(Kd_v, Kp_v, '-r')

hold off

xlabel('K_d')