Simple x-y curve fitting from data set.

I'm struggling to find a simple example of simple curve fitting in MATLAB.

I just want to do a best-fit curve for the following data:

 x = [1 1.5 2 2.5 3 10e10]
y  = [19.74 14.26 12.34 11.45 10.97 9.87];

Please could someone show me how to do it?

[Wayne King]

do you really have an x vector where the final value jumps from 3 to 10^10?

[Tom]

Well it's supposed to be infinity but yes.

Answer 1

[the cyclist]

If you type

doc polyfit

in the MATLAB command window, you will see a simple example (and of course the syntax of the command).

EDIT:

I didn't really pay attention to the, uh, unusual shape of your data. polyfit() does simple polynomial fitting, so it's not right for you.

There's not really going to be a fit for a point "at infinity". You should probably add some detail about what you are trying to really accomplish here.

[Tom]

Thanks for the response, I'm not familiar with erf so that's why I don't find it so simple and also I can't see how to apply this to my problem.

The polyfit example starts off knowing the function - erf(x) - whereas I'm starting off not knowing the function and just with a set of data points. Plotting my data doesn't give a curve of best fit - just a line graph joining the data points, which isn't what I want. Sorry if I'm missing something obvious.

[Jurgen]

By definition that line is the best fit , as it goes through every point? If you wan't more restrictions you need to decide on what form your fit must have, even if you don't know the "true" underlying function.

[the cyclist]

Tom, that example starts off with erf() simply to create the sample of data which will be fit later.

As Jurgen says, you need to decide what form you want.