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Re: st: Interpolation using cipolate


From   "joe J." <otharain@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Interpolation using cipolate
Date   Wed, 14 Apr 2004 12:30:14 +0000

Many thanks Richard. I got it now. For my yearly time series, x represents the year.



From: Richard Williams <Richard.A.Williams.5@nd.edu>
Reply-To: statalist@hsphsun2.harvard.edu
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Interpolation using cipolate
Date: Wed, 14 Apr 2004 07:14:49 -0500

At 11:41 AM 4/14/2004 +0000, you wrote:
Sorry for double posting
Dear all,

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.


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Richard Williams, Notre Dame Dept of Sociology
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