Curve fitting exponential data
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Hi all,
Hopefully someone can help me to solve this problem. It's beginning to drive me nutts.
I have an array of data and i am trying to fit a curve to the data from each column. I started firstly by looking at just a few of the curves and they appear to be of the exponential form, increasing with x to an asymptote where y goes to infinity.
the problem is that i cannot get the fit to bend correctly. i've tried using different equations but nothing gets there. this fit was done using a*exp(b*x)+c*exp(d*x).
At first i was plotting this backwards, and then the curve was fitting very well. Then i realized i needed it this way and haven't been able to get a decent fit.
I know that all of the curves from the data set have asymptotes at a values that i know.
I've also tried adjusting some of the fitting options but in all honesty i'm not sure that's helped. Nothing seems to follow the sloow increase up to the curve and then sharp turn upwards.
Any help with this or suggestions would be most greatfully appreciated.
Cheers
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the cyclist
le 6 Sep 2011
I suggest you try plotting the log of your data. That might help you infer a better fitting function.
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