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Re: st: help log linear


From   David Gottschlich <davidgottschlich@comcast.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: help log linear
Date   Sun, 22 Feb 2004 18:40:06 -0500

I seem to have gotten this a long time after you sent it, so you may have the answer already (and please forgive me if I giving the wrongly simple answer to a complex question), but....

predict logy
will give you the predicted result for each independent x; of course, this will be in log space.

If you used the natural log, then
generate predicty=exp(logy)
will convert the predictions back to real space

or
generate predicty=10^logy
works if you used the common log.

For most (many?) applications, it's more common to use the form
y=a ln(x) + b
than
ln(y)=a x + b

If you are using the second form, of course you cannot force y to equal zero unless you can reach negative infinity from your function.

David

cas2111@columbia.edu wrote:


Hi,

I am having a bit of difficulties figuring out how to predict a y
in a log linear model. I cannot determine the following items:

1)obtaining fitted values of logy(i) from the regression of logy
on each independent x
2)for each observation i, creating a variable equal to exp(logy(i))
3)performing a regression through the origin

Any other information that could be provide to assist in running a
log linear regression would be greatly appreciated.

I could not find anything in my manual about it.

Thank you,
cheryl
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