as title. I got standard curve data. According to the data sheet, I shall get a curve like sin or cos. Y-axis is normal, X-axis is log axis.
I need to solve out the curve equation so that I can calc my results.
urgent. help. thank you

do you mean: "you have a set of points (x1,y1), (x2,y2), ..., (xn,yn). you want to find a function y=f(x) such that all the points are close to the curve of y=f(x)"?

Well, I am still not sure what you want to do according to your problem statement. But generally for data-fitting, you shall
First, propose the model first (i.e. maybe in this case your sine or cosine function or whatever, for example y=AsinBx+C), use Matlab function nlinfit to find best parameter set (A,B,C);
Second, use Matlab function nlparci to find confidence interval for A,B&C respectively;
Finally, use chi2test to evaluate your model based on best-fit (A,B,C) from nlinfit. If not satisfied, propose a new model.