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AKazak

Russia
1205 Posts
Posted - 10/15/2020 :  12:15:17 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
OriginPro 2021 (64-bit) Beta 6 9.8.0.178
Windows 7 Pro x64 SP1

Greetings!

https://my.originlab.com/ftp/forum_and_kbase/Images/Exp2PMod1%20Test.opju

I fit an attached dataset with Exp2PMod1, but get the equation worse in terms of COD than that found by Excel 2013.
What would be a reason for this?
How do I improve fitting quality in Origin?

Thank you.

---
Andrey

Chris D

428 Posts
Posted - 10/15/2020 :  1:42:00 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Please see my response to a forum post from a few years ago:
https://my.originlab.com/forum/topic.asp?topic_id=19889

If I apply your data to fit it with WolframAlpha method I mention in that post, I get identical results to the results you got in Origin.


exponential fit {0.1119,6.16622},{0.1939,6.83858},{0.3022,4.9636},{0.4974,3.65903},{0.761,4.25756},{1.0045,3.54405},{2.004,1.82635},{2.9988,1.53728},{3.9991,0.40259},{5.0028,0.1819}




Thanks,
Chris Drozdowski
Originlab Technical Support
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AKazak

Russia
1205 Posts
Posted - 10/16/2020 :  08:08:24 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
quote:
Originally posted by Chris D

Please see my response to a forum post from a few years ago:
https://my.originlab.com/forum/topic.asp?topic_id=19889

If I apply your data to fit it with WolframAlpha method I mention in that post, I get identical results to the results you got in Origin.


exponential fit {0.1119,6.16622},{0.1939,6.83858},{0.3022,4.9636},{0.4974,3.65903},{0.761,4.25756},{1.0045,3.54405},{2.004,1.82635},{2.9988,1.53728},{3.9991,0.40259},{5.0028,0.1819}


Thanks,
Chris Drozdowski
Originlab Technical Support



Dear Chris,

Thank you for clarifying this.

Aaaaaa...
Excel again did something weird!

Relevant paper https://doi.org/10.1016/j.csda.2009.10.020 describes polynomial trendline function flaws in Microsoft Excel...

---
Andrey
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