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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

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

Subject |
st: RE: RE: RE: egen and spontaneously changing numbers |

Date |
Wed, 20 May 2009 18:26:32 +0100 |

The short answer I believe to be No. Whenever you are asking for a -float- result, Stata will (attempt to) give you one. That usually -- not just occasionally -- gives you less precision than is possible. What differs is that almost no-one cares about the last few decimal places if there is a fractional part, whereas we may well care about preserving integers exactly. If you want a homunculus inside the machine smart enough to work out that you are asking for something you don't really want, you may have to program it yourself, as only you know what you don't really want. More positively, these issues most commonly arise with long numeric identifiers, in which case there are two simple pieces of advice. 1. Keep all long numeric identifiers in string variables. 2. If you have a good reason not to do that, make sure that results are always specified as -long- or -double-. By the way, you can specify the default new variable type as e.g. -double-. (Specifying it as -long- would create more problems than it solved.) Nick n.j.cox@durham.ac.uk sdm1/Steve Is there any way I can get Stata to warn me that it is doing this? Nick Cox You have a precision problem. By default -egen- will generate -float- variables with the functions you are using. To keep every digit in the integers you are playing with you need to spell out that you want a -long- or -double-. There aren't enough bits in the variable type you are using. I can't follow your code which seems to go back and forth between string and numeric results, nor do I know what MEPS means. I guess there's a much simpler way to do what you want without using -egen- at all, but the issue that is biting you is illustrated thus: . set obs 1 obs was 0, now 1 . gen long myin = 40002015 . egen myout = max(myin) . egen long myout2 = max(myin) . format myout* %12.0f . l +--------------------------------+ | myin myout myout2 | |--------------------------------| 1. | 40002015 40002016 40002015 | +--------------------------------+ * * 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/

**Follow-Ups**:**st: Getting data from NBER to STATA***From:*Kirimi Sindi <sindijul@msu.edu>

**Re: st: RE: RE: RE: egen and spontaneously changing numbers***From:*Austin Nichols <austinnichols@gmail.com>

**References**:**st: egen and spontaneously changing numbers***From:*Matt Rutledge <rutledma@umich.edu>

**st: RE: egen and spontaneously changing numbers***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**st: RE: RE: egen and spontaneously changing numbers***From:*"sdm1" <sdm1@york.ac.uk>

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