Re: st: twoway lfit and time series operators

[vwiggins@stata.com (Vince Wiggins, StataCorp)]

Jorge Eduardo Perez <perez.jorge@ur.edu.co> writes that 
-twoway lfit- fails when time-series operators are applied
to the variables.

> -twoway lfit- does not work with time series operators in Stata 11.
> Is there a reason for this aside from -twoway lfit- being out of
> date?  -scatter- deals with time series operators properly.

> . sysuse sp500
> . tsset date
> . scatter l.open l5.close
> . twoway lfit l.open l5.close
>
> I had to use this workaround
>
> . gen l5close=l5.close
> . twoway lfit l.open l5close

-twoway lfit- was not intended to support time-series operators,
but the documentation is silent on this point and the error
message when operators are used is admittedly poor.

Regardless, support for time-series operators will be added to 
-twoway lfit-, -twoway lfitci-, -twoway qfit-, and -twoway qfitci- 
in a future update.

In the interim, anyone wanting to user time-series operators
with these -twoway- plottypes can use Jorge's workaround.

 
-- Vince 
   vwiggins@stata.com

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