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From |
"Steve Rothenberg" <drlead@prodigy.net.mx> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: RE: cubic spline in time series |

Date |
Mon, 13 Sep 2010 17:12:54 -0500 |

Buzz, Thanks for the tip, I remember checking out -bspline- from my ssc search. I looked again after your message and -bspline- doesn't do the trick since it only works on one variable, not two. However, at the end of the -bspline- help file it references another ssc contribution that didn't appear in the ssc search, -spline-, an oldie from Peter Sasieni, from Stata Technical Bulletin 22. -spline- takes an xvar and a yvar as arguments and the result appears to be what I'm looking for. Best, Steve Steve, Will -bspline- by Roger Newson from SSC help? ssc desc bspline Buzz Burhans, Ph.D. Dairy-Tech Group So. Albany, VT / Twin Falls ID Cell: 208-320-0829 ID Fax: 208-735-1289 VT Fax: 802-755-6842 Email: buzzb3@earthlink.net -----Mensaje original----- De: Steve Rothenberg [mailto:drlead@prodigy.net.mx] Enviado el: Monday, September 13, 2010 2:26 PM Para: 'statalist@hsphsun2.harvard.edu' Asunto: cubic spline in time series I have number of cases data per week for a multi-week time series. The data will be modeled with negative binomial models. I'd like to account for the general tendencies of the case data over time, using cubic splines and then construct the negative binomial model including the cubic splines as dependent variable smoothers, along with time-varying independent variables to determine the effect of those variables on deviations from the cubic spline-fitted dependent variable. I've used the Stata command -mkspline-, which sets spline knots according to ranges of values of a single variable. Using -mkspline- with default arguments with the dependent variable in my model, number of cases, results in four knots being placed according to increasing values of number of cases. I've searched statalist and the manuals for a spline function that takes two arguments, the variable to be fitted and another variable against which the fit should be made. The only thing I see is a Mata command -spline3_, which takes two arguments, real vector x and real vector y. This might be what I need but I've never used Mata before. I wonder if someone could help with 1. alternative ways to construct a spline fitted time function of a variable. 2. tell me if Mata -spline3- is what I'm looking for. 3. give me guidance in using either a Mata function or some other code that could do the spline fit of a variable in time. Best regards, Steve Rothenberg National Institute of Public Health Mexico * * 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/

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