How to find minimum and maximum of a fitted curve.??

I have fitter my time series using fourier option of fit command, I want to know how to find the minimum and maximum of the fitted curve

[Matt J]

You have many open threads on your profile, many of which have had responses. You should consider closing some of them unless the answers given there really didn't help you. It's hard to imagine though, that so many answers were ineffective.

[Chris Martin]

If the answer is not suitable then what can I do..

Answer 1

[Matt J]

My approach would be to,

1. Sample the curve finely (much higher sampling rate than the frequency of the fitted curve) and get approximate locations of the global max and min from the samples using the commands min() and max()
2. Refine the approximation from Step 1 using fzero. That is, use fzero to find where the derivative of the fitted curve is zero, using the points from Step 1 as the intial guesses.

[Chris Martin]

The problem is that, I am using like that f=fit(x,y,'fourier1'), I need to know the min and max of f how to get........

[Matt J]

That's what my 2-step Answer told you how to do. Use feval in Step 1, or the other methods mentioned here,

http://www.mathworks.com/help/curvefit/feval.html

to evaluate the curve at many points. When you have a vector of samples of hte curve, you can apply max() or min() to find approximate locations of the max and min. Then, in Step 2, you can refine with fzero, if you wish.

[Jan Dabrowski]

Thanks man, you helped me a lot!