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From |
Daniel Marcelino <dmsilv@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Replace |

Date |
Fri, 2 Sep 2011 20:45:11 -0400 |

Exactly that Maarten. You have killed my doubt, despite I said the 'wrong' dataset, thanks. I was just looking for an trick to set missing values with and without constraints to test some stuffs. Best Daniel On Fri, Sep 2, 2011 at 4:52 PM, Maarten Buis <maartenlbuis@gmail.com> wrote: > --- on Fri, Sep 2, 2011 at 10:29 PM, Daniel Marcelino wrote: >> I'm in doubt how I could run a loop to randomly introduce 100 missing >> values in the 'auto' dataset. > > That is easy as the auto dataset contains only 74 observations ;) > > Lets assume that you wanted exactly 20 missing observations on the variable mpg > > sysuse auto, clear > gen s = runiform() > sort s > replace mpg = . in 1/20 > > Generally I like to specify a probability of getting a missing rather > than a fixed number of missings. Below I assume you want a 20% chance > of getting a missing. > > sysuse auto, clear > replace mpg = . if runiform() < .2 > > Generalizations of this trick that will allow you let that probability > depend on other variables (e.g. to check how important the MAR, MCAR > and NMAR assumptions are) can be found in: M.L. Buis (2007b), "Stata > tip 48: Discrete uses for uniform()", The Stata Journal, 7(3), pp. > 434-435. <http://www.stata-journal.com/article.html?article=pr0032> > > Hope this helps, > Maarten > > -------------------------- > Maarten L. Buis > Institut fuer Soziologie > Universitaet Tuebingen > Wilhelmstrasse 36 > 72074 Tuebingen > Germany > > > http://www.maartenbuis.nl > -------------------------- > * > * 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/ > -- About me: http://danielmarcelino.zip.net/ * * 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: Replace***From:*Daniel Marcelino <dmsilv@gmail.com>

**Re: st: Replace***From:*Maarten Buis <maartenlbuis@gmail.com>

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