model spec 'polyijk' o=in fitlm does not work as per MATLAB documentation?
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Hi, I am trying to use 'polyijk' model spec to specify my linear regression model complexity when using fitlm, but i dont seem to be getting what the documentation suggests i should. As per documentation: 'poly13' has an intercept and x1, x2, x2^2, x2^3, x1*x2, and x1*x2^2 terms. but when i try it, the terms i get are: 1 + x1*x2 + x2^2 + x1:(x2^2) + x2^3. so somehow it is missing the x1 and x2 terms.
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the cyclist
2024년 3월 22일
편집: the cyclist
2024년 3월 22일
I think you are just misinterpreting the Wilkinson notation of the model spec in the output.
x1*x2 % note the * for interaction, which includes lower-order terms
is short-hand for
x1 + x2 + x1:x2 % note the : for interaction, which does NOT include lower-order terms
Here is an example. Note that all the terms you expect are in the table of estimated coefficients.
load carsmall
X1 = Acceleration;
X2 = Displacement;
X = [X1,X2];
y = Weight;
mdl = fitlm(X,y,"poly13")
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