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From |
David Kantor <kantor.d@att.net> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Backfill Missing Values |

Date |
Thu, 16 Apr 2009 21:04:18 -0400 |

At 07:46 PM 4/16/2009, Paul Rivera wrote:

I have a panel dataset that looks something like this: year gdpReal gdpNom gdpdefl PPI dPPI 1900 126 . . 25 1901 132 . . 27 .08 1902 138 . . 29 .074 1903 142 . . 31 .069 1904 147 41.16 28 32 .032 1905 150 48 32 34 .063 1906 151 49.83 33 35 .029 The variable I need is gdpNom. Normally, one would obtain this as: gdpNom = gdpReal * (gdpdefl/100);however, this is clearly not possible since gdpdefl is missinganywhere gdpNom is missing.So, I want to estimate gdpdefl using dPPI, something like this: gen gdpdeflFILL = F.gdpdefl/(1+F.dPPI) if gdpdefl==. gen gdpdeflEST = gdpdefl replace gdpdeflEST = gdpdeflFILL if gdpdeflEST==. This would allow me to estimate gdpNom: gen gdpNomEST = gdpnom replace gdpNomEST = gdpReal * (gdpdeflEST/100) if gdpNomEst==.BUT, my brilliant plan falls apart because the forward lag operator(F) cannot cascade the same way that the backward lag operator (L)can, so I only, for example, get an estimate for 1903.I feel like there must be an easy solution to this, but I am stuck.My panel has 57 groups and 150 time periods, so I'd much rather notdo this by hand.Any help would be much appreciated. Thanks, Paul Rivera

Possibly you should reverse the sort... gsort -year (presumably, year is a key variable) Then perform your operations, but use L. in place of F.. Afterward you can restore the original order if desired. HTH --David * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Backfill Missing Values***From:*"Rivera, Paul A." <riveraecon@gmail.com>

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