least square curve fitting

Hi

Can anyone help me to do Curve fitting with Non-linear Least Square curve fitting.

I have few points w.r.t time.. and I have to make a SINE wave with these points.

Lets say following are the values (Even though its not similar to a sinusoidal values)

 Time    Current  
 04.500   11.452
 04.525   11.528
 04.550   11.586
 04.575   11.623
 04.600   11.640
 04.625   11.638
 04.650   11.620
 04.675   11.592
 04.700   11.559

I have to make a sinusoidal curve with the help of Non Linear Least square (x = lsqnonlin(fun,x0))... the sinusoidal function can be in the form , CurrentI= A+Sin(w*Time) (with a fixed frequency lets say 200Hz)..

I know the concept of Least sqr method, but the problem is , i am not getting how to make the above function 'fun'.

Thank you.

Answer 1

[Stephen23]

fun is the function handle of the function you wish to fit to the data. It is your job to define a function of the curve you wish to fit, ensuring that it fulfills the requirements of lsqnonlin , which are explained in the documentation.

In particular, the function needs to accept an input vector, and provide an output vector which is the curve given those input values. The lsq function adjusts the input vector until the output vector best matches your given data.

You can also find explanations and examples here:

http://www.mathworks.com/help/optim/nonlinear-least-squares-curve-fitting.html

You might also like to consider using lsqcurvefit , as this "provides a convenient interface for data-fitting problems".

[Vipin Mohan]

Thnkx for the reply..

As I told, i had read thru the explanations and all...but i dont know how can i put the function handle. can i put put simply as 'A+sin(w*t)' .. its a small doubt only.A similar program will also be helpful. That is what I am expecting.3 line program code will be great .!