Curve fit for data points

Here is my code and im trying to curve fit the 5 data points and im having a hard time because they are all seperate!

figure(5)
plot(Fz_1100,Svy_1100)
scatter(Fz_1100,Svy_1100,'k');
hold on
plot(Fz_880,Svy_880)
scatter(Fz_880,Svy_880,'b');
hold on
plot(Fz_650,Svy_650)
scatter(Fz_650,Svy_650,'g');
hold on
plot(Fz_430,Svy_430)
scatter(Fz_430,Svy_430,'m');
hold on
plot(Fz_210,Svy_210)
scatter(Fz_210,Svy_210,'r');
hold on

[the cyclist]

There is way too much missing information for us to help you. (We can't read your mind.)

So many questions:

• When you say "5 data points", do you actually mean the 5 sets of data in your 5 plots?
• Do you want to fit a single curve that fits all 5 sets of data, or 5 curves (one for each set)?
• If you want 5 curves, are there any shared parameters?
• What kind of curve? Polynomial? What order polynomial?
• What's the relationship, if any, among the 5 sets of data?

You see? Lots of missing info. Help us help you.

[Cris LaPierre]

Can't help you without your data. I'm am curious is this code simplifies your plotting.

figure(5)
scatter(Fz_1100,Svy_1100,'k')
hold on
scatter(Fz_880,Svy_880,'b')
scatter(Fz_650,Svy_650,'g')
scatter(Fz_430,Svy_430,'m')
scatter(Fz_210,Svy_210,'r')
hold off

[Michael Miller]

%Inital Conditions 
Fz_1100 = 1100;
Fz_880 = 880;
Fz_650 = 650;
Fz_430 = 430;
Fz_210 = 210;
% Pacejka coefficients for 1100 N
Dy_1100 = 2633;
Cy_1100 = 2.2136;
By_1100 = -0.1086;
Ey_1100 = -.3608;
Svy_1100 =  -30.01;
% Pacejka coefficients for 880 N
Dy_880 = 2185;
Cy_880 = 2.139;
By_880 = -0.1193;
Ey_880 = 0.124;
Svy_880 = -29.52;
% Pacejka coefficients for 650 N
Dy_650 = 1721;
Cy_650 = 1.847;
By_650 = -0.1683;
Ey_650 = 0.3298;
Svy_650 = -29.02;
% Pacejka coefficients for 430 N
Dy_430 = 1212;
Cy_430 = 1.665;
By_430 = -0.1797;
Ey_430 = 0.3647;
Svy_430 = -26.3; 
% Pacejka coefficients for 210 N
Dy_210 = 638.6;
Cy_210 = 1.604;
By_210 =  -0.2165;
Ey_210 = 0.5203;
Svy_210 = -22.52;

I see what you are saying! Here is my data! I need a curve to fit those 5 data points. Therefore, when i hit run, a graph comes up with 5 points! i need a curve that fits them. I have 5 sets, but if i can do one i can do the rest. Hope that makes since.

[Michael Miller]

Also forgot to mention, the line needs to be linear!

Answer 1

[Cris LaPierre]

Here's how I would do it.

Fz = [Fz_1100 Fz_880 Fz_650 Fz_430 Fz_210];

Dy = [Dy_1100 Dy_880 Dy_650 Dy_430 Dy_210];
Cy = [Cy_1100 Cy_880 Cy_650 Cy_430 Cy_210];
By = [By_1100 By_880 By_650 By_430 By_210];
Ey = [Ey_1100 Ey_880 Ey_650 Ey_430 Ey_210];
Svy = [Svy_1100 Svy_880 Svy_650 Svy_430 Svy_210];

% Just show Svy
scatter(Fz,Svy,'k')

% fit Svy to a first order polynomial (y=m*x+b)
p=polyfit(Fz,Svy,1);
% Calculate Y values of fit line
fitY = polyval(p,Fz);

hold on
plot(Fz,fitY)
hold off

[Michael Miller]

wow! Didn't know you could do it like that! Thank you so much!