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 Fitting Plancks Law		  New Topic  Reply to Topic
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Corristo81

1 Posts
Posted - 09/27/2012 :  07:30:07 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. and Service Release (Select Help-->About Origin): Origin 8 Pro
Operating System: Windows 7

Hey,

For my advanced lab course i want to fit a Data set with a Planck curve, however if i create a new fitting function and use it to fit the data it doesn't iterate and therefore only gives out a line, where it should give the normal Planck curve: see: http://en.wikipedia.org/wiki/Planck%27s_law

the fit function is: y = (A/(x^5)) * (1/((exp(b/x))-1)) A and b are the parameters that should be fitted to our Data Values.

I'm not really used to using origin maybe someone has a beginners tutorial for complex fitting functions or something that might help me find the error?

Thanks in advance
Corristo

easwar

USA
1964 Posts
Posted - 10/02/2012 :  12:56:57 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Corristo,

I could add such a function and fit with it just fine. Note that for user-defined functions by default there is no parameter value assigned (in versions older than 8.6), so you will need to assign some initial value and then iterate. Go to the Parameters tab in NLFit dialog and put in some initial values for your parameters.

Easwar
OriginLab
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sudharajendiran

United Kingdom
2 Posts
Posted - 09/04/2015 :  12:41:49 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hiya,

I have been trying to fit the planck's curve with my continuum line and unfortunately, i could not get them correct, can someone help me in explaining them detail.

Thanks

sudha
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