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From |
Maarten buis <maartenbuis@yahoo.co.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: FW: producing value labels when value has decimal point |

Date |
Wed, 11 Aug 2010 20:50:46 +0000 (GMT) |

--- On Wed, 11/8/10, Miller, Ann C. wrote: > I have been given a float variable in which the values are > things like 1.1 ,1.2, 2.1, 2.2, 2.3. These values > correspond to diagnoses in a medical record, for example > 1.1=diarrhea, 1.2=nausea/vomiting/other GI . and so on. I > would like to create labels for this variable,but so far > have been unable. I created a program to do this (see below) > but the error message I got back was "may not label 1.1". One solution is to turn these codes into integers by mutliplying them by 10. This is a better format for storing such categorical variables like these anyhow, as integers can be stored exactly on computers while numbers like 1.1 can't. *--------------- begin example ------------- clear all input x 1.1 1.2 end lab def se_code1 /// 11 "Nausea and vomiting" /// 12"Diarrhea" gen x10 = x*10 lab val x10 se_code1 // 1.1 cannot be stored exactly, // which is the reason for the // following weird behaviour: count if x == 1.1 // here is one solution: count if x == float(1.1) // but easier is to use the // the variable where the codes // are stored as integers count if x10 == 11 *---------------- end example ----------------- (For more on examples I sent to the Statalist see: http://www.maartenbuis.nl/example_faq ) All this is related to the precision with which a number is stored on a computer. A number of great resources are: William Gould (2006) "Mata matters: precision" The Stata Journal, 6(4):550-560. http://www.stata-journal.com/article.html?article=pr0025 Nicholas J. Cox (2006) "Stata tip 33: Sweet sixteen: Hexadecimal formats and precision problems" The Stata Journal, 6(2): 282-283. http://www.stata-journal.com/article.html?article=dm0022 Jean Marie Linhart (2008) "Mata matters: Overflow, underflow and the IEEE floating-point format" The Stata Journal, 8(2): 255-268. http://www.stata-journal.com/article.html?article=pr0038 http://www.stata.com/support/faqs/data/prec.html http://www.stata.com/support/faqs/data/float.html http://www.ats.ucla.edu/stat/stata/faq/longid.htm http://www.michaelnormanmitchell.com/stow/floats-and-doubles.html 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/

**References**:**st: FW: producing value labels when value has decimal point***From:*"Miller, Ann C." <Ann_Miller@hms.harvard.edu>

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