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From |
Lars Folkestad <lfolkestad@health.sdu.dk> |

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

Subject |
Re: st: age: factor variables may not contain noninteger values |

Date |
Tue, 8 Nov 2011 12:14:16 +0100 |

This helps a lot. Thank you. But i have a question about the second point. Is there a quick and easy way to round the age to the nearest integer value? I could use the floor / ceil functions, but some of the ages Should be rounded up and some should be rounded down. lars Den 08/11/11 11.40 skrev "Maarten Buis" <maartenlbuis@gmail.com>: >On Tue, Nov 8, 2011 at 11:13 AM, Lars Folkestad wrote: >> I am trying to investigate the interactions between age and a grouping >>variable in a regression model, using this code: >> >> xi: regress Var1 age##i.group >> >> Var1: is a continuous variable >> Age: is a continous variable / float >> >> When i run the code i get the following error message: >> age: factor variables may not contain noninteger values > >First, you are mixing -xi- and factor variable notation. You should >just leave the -xi:- prefix away. > >Second, in most surveys I am aware of age will be measured in whole >years. In those cases age should only contain integer values and this >error message means I made an error while preparing the data. This is >true regardless of how the data is stored. However, this is not >necessarily an error, you could have fractional age if you had for >instance exact birth dates and exact dates at which events of interest >happen. Alternatively, I may have standardized age or rescaled it so >it is measured in decades rather than years. However, in the latter >two cases I would have created new with different variable names >(probably z_age and age_d). So I would check whether non-integer age >would make sense given the way your data was collected. > >Third, whether there is an error or not you probably want -regress >var1 c.age##i.group- i.e. tread age as a continuous variable and not >as a set of dummies. > >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/ * * 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**:**RE: st: age: factor variables may not contain noninteger values***From:*"Jesper Lindhardsen" <JESLIN01@geh.regionh.dk>

**References**:**Re: st: age: factor variables may not contain noninteger values***From:*Maarten Buis <maartenlbuis@gmail.com>

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