I have seen that a polynomial linear regression can have this form:
$y = c_0 + c_1 x_1 + c_2 x_2 + \dots + c_k x_k $
but I have read that the general lineal model which is a form of the multiple linear regression, can have this form:
I see that almost both of them are the same. When I program in R the second case, I can use the function abline, that draws a line of "best fit" as it is called. But when I want to use it in the first case (the polynomial one) it is not possible. Why is that? If both returns a set of scattered points over the plane
Examples of both cases:
First case it could be the index of houses bought by clients over years and bimonthly. Second case, a classical one, it would be the weight prediction of a person considering the weight of their hips, arms, etc.
Why I can use abline in the second case, but not in the first one?