Polynomial curve fitting--how to use cubic

I have this code:x=[1.69,1.99,1.99,1.99,1.99,1.99,2.70,2.70,2.70,3.00,3.00,3.00,3.00,3.37,3.37]; plot(x,'r-'); I use the tool "Figure"-"Tools\Basic Fitting"-"cubic" to do the Polynomial curve fitting,but I don't know how to write down the code about "cubic",it's grateful if somebody can help me.

Answer 1

[Matt Fig]

Do you mean, how to get the coefficients from the command line?

PP = polyfit(1:length(x),x,3);

EDIT

To plot the polynomial, use:

hold on
xp = linspace(1,length(x),100);
yp = polyval(PP,xp);
plot(xp,yp,'b-')

[Tian Lin]

thank you,I know how to get the coefficients by "polyfit",but I don't know how to write some words to plot the Polynomial curve. I have already tried "polyval",but it did not work very effectivly.

[Walter Roberson]

xi = 0:.1:length(x);

plot(xi, polyval(PP,xi));

[Tian Lin]

it's ok,I get it,thanks,gays

[Jan]

I'm not a native speaker, but I have the strong impression that there is a difference between "guys" and "gays".

If Matt Fig's answer solves your problem, please accept it.

[Tian Lin]

sorry,man,it's just a cacography.I will accept the answer