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From |
"joe J." <otharain@hotmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
RE: st: Interpolation using cipolate |

Date |
Wed, 14 Apr 2004 20:24:36 +0000 |

I very much appreciate your response as it makes me doubly sure that what I understood about -cipolate- is correct (given that you authored the programme). I already had a trial run and find it extremely suited for the job in hand. I am sorry that I did not mention that it is a user-written programme. Shall be careful next time.

Joe

_________________________________________________________________From: "Nick Cox" <n.j.cox@durham.ac.uk> Reply-To: statalist@hsphsun2.harvard.edu To: <statalist@hsphsun2.harvard.edu> Subject: RE: st: Interpolation using cipolate Date: Wed, 14 Apr 2004 21:06:35 +0100 Good. But others might appreciate the explanation of what -cipolate- is. Among other advice, the Statalist FAQ suggests Say what command(s) you are using. If they are not part of official Stata, say where they come from: the STB/SJ, SSC, or other archives. Nick n.j.cox@durham.ac.uk joe J. > Thanks Nick. I got the awakening when Richard gave the reply. > > >-cipolate- is a user-written command on SSC for cubic > >interpolation. As Richard surmises, the logic is that > >you must interpolate gaps in a response with respect > >to a second variable (e.g. time), just as with official > >Stata's -ipolate-, which is for linear interpolation. > > > >Richard Williams replied to Joe J. > > > > > >A naive question. I just insalled cipolate to fill missing > > > values for one > > > >variable. The documentation tells me that interpolation is > > > done using two > > > >points before and two points after the missing value. That > > > said, why is it > > > >that the procedure requires a second variable? In other > words, for > > > >replacing missing values in variable y, why we need to > > > include variable x > > > >in the command? > > > > > > > >. cipolate y x, gen(yprime). > > > > > I don't know about -cipolate-, but the docs for -ipolate- > > > (reference manual > > > G-M, pp. 182-183) say that Y is a function of X. The value for > > > interpolated Y is computed using values from the surrounding > > > Xs and Ys that > > > are not missing. > > > > > > If you are going to interpolate, your data have to be sorted > > > in some way, > > > right? So having an X accomplishes that. The distance > > > between Xs will be > > > related to the interpolated differences between Ys. * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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