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From |
"Klaus Pforr" <kpforr@googlemail.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: AW: lag |

Date |
Thu, 31 May 2012 11:06:00 +0200 |

<> Dear Fabian, I think that are correctly expecting that "sale[_n-4]" is missing for the first for observations. The problem is, that "sale[_n-4]" is evaluated as "." for _n<=4, but the boolean expression "sale<=sale[_n-4]" is - at least not necessarily - evaluated as missing for these obs. As sale is probably less than the pseudo-infinitely large "." (See: help missing), you will have "sale_decrease5=1" for these observations. To catch this problem, you can add the assertion "& sale[_n-4]!=." to you if-condition. best Klaus __________________________________ Klaus Pforr GESIS -- Leibniz Institut für Sozialwissenschaft B2,1 Postfach 122155 D - 68072 Mannheim Tel: +49 621 1246 298 Fax: +49 621 1246 100 E-Mail: klaus.pforr@gesis.org __________________________________ -----Ursprüngliche Nachricht----- Von: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von "Fabian Schönenberger" Gesendet: Donnerstag, 31. Mai 2012 10:52 An: statalist@hsphsun2.harvard.edu Betreff: st: lag Dear Statalist With the following command I want to generate a dummy variable; 1 if current sales are lower than 4 years ago, 0 if sales are larger for each company: by cusip: generate sale_decrease5=0 if sale>sale[_n-4] by cusip: replace sale_decrease5=1 if sale<=sale[_n-4] I expected for each cusip 4 missings at the beginning, since there is no _n-4. However, the command gives 1 for each cusip in the first four years. How do I have to adapt the formula to get dummy variables after the first 4 years passed? Many thanks in advance. Fabian -- NEU: FreePhone 3-fach-Flat mit kostenlosem Smartphone! Jetzt informieren: http://mobile.1und1.de/?ac=OM.PW.PW003K20328T7073a * * 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/ * * 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: lag***From:*"Fabian Schönenberger" <sch.f@gmx.ch>

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