Re: st: RE: Linear Regression

[Steven Samuels <sjhsamuels@earthlink.net>]

Someone from StataCorp recently noted that it can be done with -nl-

/*******************************************/
sysuse auto
nl (mpg = {b0}+ {b1}*weight + {b2}*weight^2)
/********************************************/

No program with which I am familiar (SAS, R, SPSS, Stata) allows the  
simpler syntax that Meric would like to use. Either one must create a  
new variable or create names for all coefficients and supply them to  
the equation.  If Meric is concerned about the effort of adding many  
polynomial terms, then -orthpoly- would be an easy approach.


-Steve


On Aug 8, 2008, at 9:39 AM, Nick Cox wrote:


> I am not clear what your question is precisely.
>
> But if you want to -regress- on something and its square, you need to
> -generate- the square as a new variable before you can do it,  
> unless it
> exists already.
>
> I am not clear what you mean by "efficient", but I don't think  
> there is
> another way to do it.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Meric Osman
>
> I have a problem about writing my regression equation. I want to add
> the variable and its square at the same time. Such as
>
> y = a + a^2 + ...
>
> Actually, I can do it by generating a new variable which is a*a, but I
> don't wanna do that because it is not an efficient way.
>
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