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Re: st: duplicated datetime variable differs from original datetime variable it was derived from
From
Nick Cox <[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 13:45:30 +0000
We are collectively and individually pretty confused about your
situation. Your original post implied clearly that -time1- was a
float; now you say it's a double.
To make progress, we need one and ideally all of the following:
1. A more complete statement of your code.
2. A more complete description of your data.
3. Code that can be replicated by others.
Nick
[email protected]
On 12 November 2013 13:12, Sergiy Radyakin <[email protected]> wrote:
> 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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