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 Getting different values from gaussian fits		  New Topic  Reply to Topic
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CoreyUofS

2 Posts
Posted - 06/21/2011 :  12:50:15 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. and Service Release (Select Help-->About Origin): 7.5
Operating System: Windows XP Professional

Hello,

I'm working with a spectrum that has two gaussian peaks. When I use the advance fitting tool it gives me the following data:

quote:
Data: SData_Absor
Model: Gauss
Equation: y=y0 + (A/(w*sqrt(PI/2)))*exp(-2*((x-xc)/w)^2)
Weighting:
y No weighting

Chi^2/DoF = 0.00002
R^2 = 0.99876

y0 -0.0006 +- 0.00019
xc1 24180.94485 +- 0.8721
w1 842.53435 +- 1.86169
A1 442.93433 +- 0.90827
xc2 25162.82595 +- 10.22823
w2 498.01928 +- 19.32544
A2 16.59963 +- 0.73356


Now when I integrate the two guassian peaks the fitting tool out puts I get this data:

quote:
Peak 1
Area------------Peak at---------Width-----------Height
439.62129-------24178.56081-----992.65028-------0.41885
Peak 2
Area------------Peak at---------Width-----------Height
13.29298--------25200.71365-----583.76082-------0.02568


My problem is, how come the w1 is not the same as the width for peak 1 and w2 is not the same as the width for peak 2?

I used my calculator to manually figure out the width and the values from integrating seem to be the correct ones.

CoreyUofS

2 Posts
Posted - 06/21/2011 :  1:16:50 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
When I looked a bit closer I found w wasn't the width, it was about 0.849 the width since it was width times sigma.

Problem solved :)
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easwar

USA
1964 Posts
Posted - 06/21/2011 :  4:30:21 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

In recent versions of Origin, we added feature of Derived Parameter, so one can define new parameters based on the fitting parameter values, and those will be reported in the results/report sheet. So for example, with Gaussian, FWHM is defined as a derived parameter. Users can add more derived parameters to built-in and user-defined functions.

Easwar
OriginLab
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