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Re: st: duplicated datetime variable differs from original datetime variable it was derived from
From
Sergiy Radyakin <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: duplicated datetime variable differs from original datetime variable it was derived from
Date
Tue, 12 Nov 2013 08:12:40 -0500
Milena, you have shown us your syntax
gen time1=time
Contrary to your expectation you are not creating a duplicate
variable. You are creating a new variable of type FLOAT which would
hold the result of the computation, which happens to be just value of
another variable. Whatever that variable is, byte or double, Stata
would compute the result and store into a float, and in your case
loose precision.
To create a proper duplicate, use -clonevar-.
To confirm the types of the variables, use -describe-.
Best, Sergiy Radyakin
On Tue, Nov 12, 2013 at 7:34 AM, Milena Przheska
<[email protected]> wrote:
> I don't think so.
> The original time variable was obtained with the MySQL function
> FROM_UNIXTIME() and Stata automatically read it as a double.
> The reason I duplicated the variable is so I break ties between events
> that had same time stamp, without altering the original data.
> Maybe something in this process created the problem, but I did not use
> -float- type at all.
>
> On Tue, Nov 12, 2013 at 1:26 PM, Nick Cox <[email protected]> wrote:
>> My guess: you copied a -float- into a -double-. Doing that won't
>> restore the precision lost in using a -float- in the first place. It's
>> blown away in the wind, washed downriver.
>> Nick
>> [email protected]
>>
>>
>> On 12 November 2013 12:01, Milena Przheska
>> <[email protected]> wrote:
>>> The problem is that my time1 variable is double, and yet, when using
>>> it in the model, it gives that error message
>>>
>>> On Tue, Nov 12, 2013 at 12:54 PM, Nick Cox <[email protected]> wrote:
>>>> Same answer. Use a -double-.
>>>>
>>>> Nick
>>>> [email protected]
>>>>
>>>>
>>>> On 12 November 2013 11:51, Milena Przheska
>>>> <[email protected]> wrote:
>>>>> When I try to fit a mixed effects model with the time1 variable as
>>>>> defined above, I get an error message "time variable must be
>>>>> integer-valued".
>>>>>
>>>>> I do need the time variable to be by the second, otherwise I will have
>>>>> duplicate values for the time variable.
>>>>>
>>>>> If you have any suggestions, I would very much appreciate it.
>>>>>
>>>>> Thank you,
>>>>> Milena
>>>>>
>>>>> On Tue, Nov 12, 2013 at 12:41 PM, Nick Cox <[email protected]> wrote:
>>>>>> Phil has the answer in one. Unfortunately, you do have to keep
>>>>>> remembering that a date-time to Stata is just an integer, usually
>>>>>> large, giving time in milliseconds.
>>>>>>
>>>>>> . di %14.0f clock("07jun2012 03:11:48", "DMYhms")
>>>>>> 1654657908000
>>>>>>
>>>>>> Numbers that big have to be stored as -double-s.
>>>>>> Nick
>>>>>> [email protected]
>>>>>>
>>>>>>
>>>>>> On 12 November 2013 11:33, Phil Clayton <[email protected]> wrote:
>>>>>>> Dates with times need to be stored in double precision. Try:
>>>>>>> gen double time1=time
>>>>>>>
>>>>>>> See -help datetime-
>>>>>>>
>>>>>>> Phil
>>>>>>>
>>>>>>> On 12 Nov 2013, at 10:25 pm, Milena Przheska <[email protected]> wrote:
>>>>>>>
>>>>>>>> Dear Statalist members,
>>>>>>>>
>>>>>>>> When duplicating a time variable by typing
>>>>>>>>
>>>>>>>> gen time1 =time
>>>>>>>>
>>>>>>>> the new variable time1 is off by several seconds from the variable time, so
>>>>>>>>
>>>>>>>> time
>>>>>>>> 06jun2012 22:44:51
>>>>>>>> 06jun2012 22:44:54
>>>>>>>> 06jun2012 22:44:56
>>>>>>>> 07jun2012 01:39:58
>>>>>>>> 07jun2012 01:40:05
>>>>>>>> 07jun2012 01:40:45
>>>>>>>> 07jun2012 03:09:48
>>>>>>>> 07jun2012 03:09:48
>>>>>>>> 07jun2012 03:11:06
>>>>>>>>
>>>>>>>> becomes
>>>>>>>>
>>>>>>>> time1
>>>>>>>> 06jun2012 22:45:17
>>>>>>>> 06jun2012 22:45:17
>>>>>>>> 06jun2012 22:45:17
>>>>>>>> 07jun2012 01:40:03
>>>>>>>> 07jun2012 01:40:03
>>>>>>>> 07jun2012 01:40:03
>>>>>>>> 07jun2012 03:09:37
>>>>>>>> 07jun2012 03:09:37
>>>>>>>> 07jun2012 03:11:48
>>>>>>>>
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