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From | natasha agarwal <agarwana2@googlemail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: RE: RE: estimation with a time trend. |
Date | Mon, 5 Jul 2010 13:45:16 +0100 |
On Mon, Jul 5, 2010 at 1:14 PM, Maarten buis <maartenbuis@yahoo.co.uk> wrote: > --- On Mon, 5/7/10, natasha agarwal wrote: >> I am afraid I did not understand "year- (or -year- >> MINUS> midpoint) for interpretability?" > > Say you have a variable representing year of birth > ranging between 1910 and 1980. I would then usually > have a line like this in my do-file: > > gen c_year = year - 1910 > > Afterwards I would use c_year instead of year. In > this case "midpoint" is 1910, and makes sure that > your new variable is shifted to the left such that > it has the value zero in 1910. This makes sure > that the baseline in your models refer to a point > at the beginning of your observed period. This is > particularly important if you include interactions > or if you care about the constant (e.g. in a random > effects model) I am estimating the model with a within estimator. I thought that they mean center the data anyways? > Hope this helps, > Maarten > > -------------------------- > Maarten L. Buis > Institut fuer Soziologie > Universitaet Tuebingen > Wilhelmstrasse 36 > 72074 Tuebingen > Germany > > http://www.maartenbuis.nl > -------------------------- > > > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/