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Subject: Partial curve fitting
Date: Sun, 24 May 2009 23:29:02 +0000 (UTC)
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Hi,

It might be a bit stupid question, but I've started to use curve fitting toolbox, and I wonder if there is a way to fit a specially formed curve to only a part of the data points, without knowing beforehand wich part to fit.
To make it a bit more clear, what I want to do:
I have a series of data points, say this graph:
 [URL=http://img162.imagevenue.com/img.php?image=06948_example_122_869lo.jpg][IMG]http://img162.imagevenue.com/loc869/th_06948_example_122_869lo.jpg[/IMG][/URL]
Now I want to decompose this, to specific curves, in these forms:
 [URL=http://img257.imagevenue.com/img.php?image=06953_effects_122_531lo.jpg][IMG]http://img257.imagevenue.com/loc531/th_06953_effects_122_531lo.jpg[/IMG][/URL]
But I don't want to specify the beginning and the end of the different curves, I want the program to find those automatically.
So I run curve fitting, and what I get is the following:
 [URL=http://img109.imagevenue.com/img.php?image=07229_example_2_122_1191lo.jpg][IMG]http://img109.imagevenue.com/loc1191/th_07229_example_2_122_1191lo.jpg[/IMG][/URL]
 And I get this, because it tries to fit the curve to the whole data set. But what I want is a function, that fits better on a part of it, where the function not equals 0.5 and I don't care how it fits, where the function is 0.5. I could easily do this, If I would just cut out that part, where I want to achieve a better fit. But then the decomposition would not be automatic. 
I hope someone can help. Thanks for any advice.