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sundywei

USA
1 Posts
Posted - 04/25/2012 :  5:31:04 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hello,

I have a question on the multiple decay components weight calculation. The NL curve fitting equation I'm using is y = y0 + A1*exp(-(x-x0)/t1) + A2*exp(-(x-x0)/t2), after I got t1 and t2, how to calculate their weight/ratio?

Normally I use A1/(A1+A2) to calculate the weight of t1, but I doubt the accuracy of it. Is anyone familiar with the weight/ratio calculation? Thank you very much!

Hua

Sam Fang

293 Posts
Posted - 04/26/2012 :  04:26:03 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
I don't know the definition of the weight of t1. If it is A1/(A1+A2), then there are two methods.

Method1:
In Origin 8.6, you can specify the weight of t1 as a Derived Parameter.

Method2:
You can also specify the weight of t1 as a fitting parameter, i.e.

y = y0 + A*(p*exp(-(x-x0)/t1) + (1-p)*exp(-(x-x0)/t2))

where p is the weight of t1.

Generally the two methods should get the same result.

Sam
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