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altomare

USA
19 Posts
Posted - 06/20/2001 :  3:11:08 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi all,
I have a question about a fit and I hope someone can help me.
I have to fit some experimental data to the derivative of the log of a gamma function.
gammaln(x)=ln(gamma(x)) is already defined, but how can I have a fit to its derivative?
Thanks a lot
Fabio

PS I'm using origin 6.0 (not the professional edition)

Edited by - altomare on 06/20/2001 15:25:49

greg

USA
1380 Posts
Posted - 06/25/2001 :  11:18:55 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
There is an example of using LabTalk's Integrate command within a fitting function:

http://www.originlab.com/www/support/resultstech.asp?ItemID=121

Fitting with Integrals
, but I don't think that will help much. Origin does not do abtract math so a differentiation in this case would only be of discrete values - complicated by the fact that the derivative command (our discrete differentiation) will alter the dataset on which it operates (so you need a copy) and needs to be associated with the same X dataset as the original data.

Maybe consulting a calculus book will give you the functional form of what you seek which you can implement as a new function in Origin.



Edited by - greg on 06/25/2001 11:23:04
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altomare

USA
19 Posts
Posted - 06/28/2001 :  5:51:32 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
HI Greg,
thanks a lot for your answer: since there was nothing in the help I kind of suspected it.
I'm just wondering however if I can create an external function with Origin Professional (I may have access to an older version) and use it somehow. I have no idea if I can, I'm just contemplating the hipotesys. Would it be possible?
Thanks
Fabio
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