Multiple Linear Regression; Terms in X
1 view (last 30 days)
Show older comments
I would like to ask why in the carsmall example X has the extra term x1.*x2, like this:
X = [ones(size(x1)) x1 x2 x1.*x2];
Running b = regress(y,X) returns
b = 4×1
60.7104
-0.0102
-0.1882
0.0000
which means that eitherway the last term plays no role.
Thanks :)
0 Comments
Answers (1)
Benjamin Thompson
on 25 Jan 2022
It is a bilinear fit so the regression is attempting to find the optimal b vector that fits a two-input function F of X and Y:
YFIT = b(1) + b(2)*X1FIT + b(3)*X2FIT + b(4)*X1FIT.*X2FIT;
Hence, the ones in the first column of X in your example since that is the constant. This technique can also be used to fit to polynomial functions and other nonlinear functions as long as the problem is linear in the coefficients you solve for.
See Also
Categories
Find more on Regression in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!