Thanks to Kit Baum, working for your benefit on 4 July,
a package -cipolate- has been added to SSC. Here is
an executive summary:
-cipolate-
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.
Nick
[email protected]
*
* 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/
