Re: st: Interpolation using cipolate

[Richard Williams <Richard.A.Williams.5@nd.edu>]

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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