MATLAB: Fitnlm and dumthe variables

dummy variablesfitnlm

Hi all, Fitnlm allows automatic creation of dummy variables, if one input the categorical predictor as a nominal or ordinal array. It worked fine for me with fitlm. But I do not understand how I know how many input arguments I get after using the automatic creation of dummy variables. As I need to specify my beta0 I need to know how many input arguments I have. Thank you!

Best Answer

I haven't used the automatic creation of dummy variables, so I don't know the answer to your question. However, the dummyvar() function might also be helpful for you, so I thought I'd mention it.

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MATLAB: Multiple Linear Regression using fitlm function

In a linear regression of any sort, there is only one intercept.

MATLAB: Interaction dummies

Here is a specific example of how to do it. If you need to generalize it and can't figure that out, let me know. The idea is to multiply the first column of d1 by each column of d2, then the second column of d1 by each column of d2:

d1 = dummyvar(T); d2 = dummyvar(R);
d1(:,[1 1 1 2 2 2]).*d2(:,[1 2 3 1 2 3])

Another thing to consider is the x2fx function, using something like this:

x2fx([T R],'interaction',1:2)

This requests that both T and R be treated as categorical, and that all columns for an interaction model be computed. You'll see the result has a column of ones, then dummy columns for T and R separately, then columns for the interaction. The idea is that these will be used in regression, so certain columns are omitted so that the full matrix is not overdetermined.

Best Answer

Related Solutions

MATLAB: Multiple Linear Regression using fitlm function

MATLAB: Interaction dummies

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