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 Differences between R square and R value.		  New Topic  Reply to Topic
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jd0331

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Posted - 08/18/2009 :  01:27:44 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
Operating System: Win xp

Hi, I performed NLfit and got R square and R value.
I know that they represent the goodness of fitting.
What I wonder is that I do not understand the differences between R square and R value.
I checked Origin tutorial, and R value is the square root of R square, which means R square is equal to the R value.
However, the final R square and R value results that I got after NLfit were different.
Could you explain the differences to me if you know why please?

By the way, I found that the reduced chi^2 is the chi^2 devided by Degree of freedom.
What is Dof?
Is it the number of data apoints?
If so, why the Dof is different from that of my datapoints?

Thanks.

larry_lan

China
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Posted - 08/18/2009 :  02:34:29 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi:

This Link can help.

R square = (R value)*(R value).

See equation (20), (22). And DOF means Degree of Freedom, which equals to (n-p) here. Where n is the number of data points and p is the number of parameters. See equation (4).

Thanks
Larry
OriginLab Technical Services
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