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From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

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

Date |
Tue, 8 Nov 2011 11:40:25 +0100 |

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/

**Follow-Ups**:**Re: st: age: factor variables may not contain noninteger values***From:*Lars Folkestad <lfolkestad@health.sdu.dk>

**References**:**st: age: factor variables may not contain noninteger values***From:*Lars Folkestad <lfolkestad@health.sdu.dk>

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