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 2 stage power fit don't converge		  New Topic  Reply to Topic
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Tasoscave

United Kingdom
2 Posts
Posted - 08/02/2017 :  03:55:25 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi, I am trying to fit a simple power curve in a 2-stage data set.

The data are composed from two stages which means I need to fit a power fir curve twice.

The first curve (1st stage) has a perfect match.
However, the second (2nd stage) is not converging and I need to normalize the data back to zero in order to have a good fit.

Any help will be much appreciated

AmandaLu

439 Posts
Posted - 08/02/2017 :  06:51:28 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

Please send your data to tech@originlab.com. Maybe the initial values are not good so the fit did not converge.

Thanks,
Amanda
OriginLab Technical Service
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Hideo Fujii

USA
1582 Posts
Posted - 08/02/2017 :  09:41:45 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Tasoscave,

> I need to normalize the data back to zero in order to have a good fit.

You are using Allometric1 function which doesn't have the bias terms. Have you tried Power0 function
(under Power category) which has both X and Y biases (xc and y0)? You can normalize the data by
subtracting these values later, if you need.

--Hideo Fujii
OriginLab
Edited by - Hideo Fujii on 08/02/2017 09:42:26 AM
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