Curve fitting with more than 3 variables

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!

[Mahdi]

Do you mean you want to do it in a higher dimension than 3D? Or more polynomial coefficients?

Answer 1

[dpb]

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.

Answer 2

[dpb]

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

https://www.moresteam.com/whitepapers/download/dummy-variables.pdf

For setting up contrasts between more locations, there are some restrictions on the dummy encoding. Any good text on regression will address it.

[Tania]

Would it make more sense to use decision trees instead of dummy variables for a postcode variable? Thank you!

[dpb]

"More", I don't know would be a good way to put it; it's an alternative choice, yes. I really have no direct experience in the specific area of regression trees, sorry.

Don't know you've anything to lose by trying both and seeing which does a better job for your purposes on the data you have. You'll want to avoid making any generic conclusions from just a sample dataset results, obviously...

[Tania]

ok great, thank you for your answer. I might try both.

Answer 3

[Tania]

Thanks thats great!

[Image Analyst]

Go ahead and "Thank" him by officially "Accepting" and voting for his answers.

[essa mohammed]

????

[John D'Errico]

I unaccepted this self answer, and accepted the Answer from dpb instead.

Answer 4

[ehsan brtn]

still i didn't find the answer