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From |
Chris Witte <eljefespeaks@yahoo.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: using coefficients from model |

Date |
Mon, 30 Mar 2009 13:33:29 -0700 (PDT) |

Maarten, I want to report the regression equation in my manuscript so the reader can plug in their independent variable values and get the correct estimate. I thought that calculating the difference between the _fracpred_ estimated values and the values estimated using the coefficients from the _fracpoly_ output would be the fastest way to find the "real" constant for reporting purposes. Is there a better (i.e. easier) way? Am I misunderstanding the process? Chris ----- Original Message ---- From: Maarten buis <maartenbuis@yahoo.co.uk> To: statalist@hsphsun2.harvard.edu Sent: Monday, March 30, 2009 3:09:57 PM Subject: Re: st: using coefficients from model You can access the parameter estimates using _b[varname], but I don't understand why you would want to do this. Isn't it much easier to just read the manual entry for -fracpoly-? This extensively documents how the variables are transformed. -- Maarten ----------------------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://home.fsw.vu.nl/m.buis/ ----------------------------------------- --- On Mon, 30/3/09, Chris Witte <eljefespeaks@yahoo.com> wrote: > From: Chris Witte <eljefespeaks@yahoo.com> > Subject: st: using coefficients from model > To: statalist@hsphsun2.harvard.edu > Date: Monday, 30 March, 2009, 8:55 PM > I am using stata 9.2. I would like to know how to call > the coefficients from the estimation results matrix e(b) and > use them in an equation. For example, if my matrix e(b) > has values for "_cons" and coefficient > "test", I would like to calculate the answer to an > equation y = [_cons] + x*[test]. How can I do this? > > The reason why I want to do this is because I am trying to > find the value _fracpoly_ adjusts its estimates by. If I > use this output from my _fracpoly_ estimation: > > study1twsg Coef. Std. Err. > t P>t [95% Conf. Interval] > Itemp__1 15093.12 4454.121 3.39 > 0.012 4560.802 25625.45 > Itemp__2 -10666.18 3136.84 -3.40 > 0.011 -18083.63 -3248.734 > Itemp__3 1945.114 569.9302 3.41 > 0.011 597.4436 3292.785 > _cons .0053322 .0008244 6.47 > 0.000 .0033828 .0072815 > Deviance: -113.24. Best powers of temp among 164 models > fit: -2 -2 -2. > > and I plug in these coefficients with my 'x' > having a value of 25, my linear regression equation for > predicting y is: > > y=.0053322+(15093.12*25^-2)+(-10666.18*25^-2*log(25))+1945.114*25^-2*(log(25))^2 > > However, this equation does not yield the same value as > _predict_ (or _fracpred_), and this is because fracpoly > secretly adjusts its constant. If I can calculate the > answer to this equation and put it into a variable, I can > then find the difference between this variable and the value > that _fracpred_ gives. > > Thank you for your help. Hopefully this isn't too > confusing. > > Chris > > > > > > * > * 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/ * * 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/

**References**:**Re: st: using coefficients from model***From:*Maarten buis <maartenbuis@yahoo.co.uk>

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