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

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

Subject |
st: cubic spline in time series |

Date |
Mon, 13 Sep 2010 14:25:41 -0500 |

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/

**Follow-Ups**:**st: RE: cubic spline in time series***From:*"Buzz Burhans" <buzzb3@earthlink.net>

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