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Curve fitting with more than 3 variables

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Tania
Tania on 4 Jun 2014
Commented: John D'Errico on 2 Dec 2018
Hi! I am doing curve fitting with matlab at the moment and would like to do it with more than 3 variables.Is that possible and how can i do it? please see the screenshot, I can not add any further variables there. Thank you!
  1 Comment
Mahdi
Mahdi on 4 Jun 2014
Do you mean you want to do it in a higher dimension than 3D? Or more polynomial coefficients?

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Accepted Answer

dpb
dpb on 4 Jun 2014
That's correct; the cftool GUI is limited to curves or surfaces.
You can define other more general models you wish with with either GeneralizedLinearModels tools in the Statistics Toolbox (under 'regression') or can always write the normal equations directly and use the backslash ("\") operator to solve.
Details on what your inputs are and the desired model could lead to more specific responses.

More Answers (3)

dpb
dpb on 5 Jun 2014
Edited: dpb on 5 Jun 2014
Don't know about web sites; the Matlab doc starts under
doc
Open the Statistics Toolbox section, select "Regression and Classification" and then "Parametric Regression". Start at the bottom with the Concepts section and work your way thru to the Linear Models which is probably all you need.
ADDENDUM:
There's a little more to it than the following, but the general idea for indicator variables is easily seen in the following
For setting up contrasts between more locations, there are some restrictions on the dummy encoding. Any good text on regression will address it.
  3 Comments
Tania
Tania on 13 Jun 2014
ok great, thank you for your answer. I might try both.

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Tania
Tania on 7 Jun 2014
Thanks thats great!
  3 Comments
John D'Errico
John D'Errico on 2 Dec 2018
I unaccepted this self answer, and accepted the Answer from dpb instead.

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