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


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: age: factor variables may not contain noninteger values
Date   Tue, 8 Nov 2011 19:39:44 +0000

All that said, as age as an integer usually means "age last birthday",
I am surprised that -round()- is regarded as the answer. I would put
my foot down for -floor()-.

For example, I am 19 and will not be 20 until next birthday.

Nick

On Tue, Nov 8, 2011 at 7:29 PM, Lars Folkestad <lfolkestad@health.sdu.dk> wrote:
> Thank you for that jesper. It sure did the trick.
> lars
>
> Den 08/11/11 13.17 skrev "Jesper Lindhardsen" <JESLIN01@geh.regionh.dk>:
>
>>Hi Lars,
>>
>>Try
>>
>>
>>g new_age= round(age_var,1)
>>
>>
>>HTH,
>>
>>Jesper
>>
>>-----Original Message-----
>>From: owner-statalist@hsphsun2.harvard.edu
>>[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Lars
>>Folkestad
>>Sent: 08 November 2011 12:14
>>To: statalist@hsphsun2.harvard.edu
>>Subject: Re: st: age: factor variables may not contain noninteger values
>>
>>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
>>>--------------------------
>>>
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