Monday, January 02, 2006

RE: st: Efficiency of calculating maximum likelihood

Hi Steinar,

My initial guess was you could use the previous estimates as starting values. It might speed things up, but as the example below shows, that does not have to be. In the example the model with starting values needed more itterations than the model without.

*------------begin example-------------- sysuse cancer, clear stset studytime, failure(died) xi: streg i.drug age, dist(lnorm) matrix b0 = e(b) xi: streg i.drug , dist(lnorm) from(b0, skip) xi: streg i.drug , dist(lnorm) *-------------end example-----------------

HTH, Maarten

----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands

visiting adress: Buitenveldertselaan 3 (Metropolitan), room Z214

+31 20 5986715

http://home.fsw.vu.nl/m.buis/ -----------------------------------------

Steinar Fossedal wrote: > I'm trying to fit a model using stepwise selection, and so I > reestimate fairly similar models over and over. Fitting a model > using -streg- takes about an hour using my dataset. I noticed > that two thirds of the calculation time is spent calculating > the constant-only model - which is exactly the same for all the > estimations. Is there any way of making stata use the results > of previous calculations to save time in this process?

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