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st: -cipolate- now on SSC

From   "Nick Cox" <[email protected]>
To   <[email protected]>
Subject   st: -cipolate- now on SSC
Date   Thu, 4 Jul 2002 18:32:43 +0100

Thanks to Kit Baum, working for your benefit on 4 July,
a package -cipolate- has been added to SSC. Here is 
an executive summary: 


Stata module for cubic interpolation

-cipolate- creates newvar = yvar where yvar is not missing 
and fills in newvar with cubicly interpolated values of yvar 
where yvar is missing. Interpolated values are based on exact 
fitting of a cubic curve to two data points before and two 
data points after each observation for which yvar is missing. 
-cipolate- will thus produce missing values whenever fewer than 
two data points are present on either side. Note that this is not a
spline method. Extrapolation is not provided, mainly because of 
reservations about the general (and even particular) wisdom of 
extrapolating cubics into the unknown. Some users may wish to 
extrapolate any remaining missing values linearly using -ipolate-.

The mathematics are due to Lagrange, but then one can multiply 
examples of his contributions. 

Stata 7 is required. 

To install, type 

ssc inst cipolate

in an up-to-date Stata. If that last sentence is obscure, 
please consult the -findit- FAQ cited below my signature. 

[email protected] 
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