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Re: st: Looping over datetimes for simultaneous variable generation


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Looping over datetimes for simultaneous variable generation
Date   Thu, 3 Oct 2013 10:48:13 +0100

There are several problems evident here, and I guess some latent too.

You don't refer to any `datetime' macro within the loop, so at best it
would do the same things, regardless of the loop.

The syntax ' ' means nothing to Stata. You may wish to evaluate
numeric constants on the fly, for which the syntax would be something
like  `=  tc(19aug2012 0:00:00)’

The constant tc(00:05:00) seems unlikely to be what you intend.

For an arbitrary numlist you need -foreach- not -forvalues-.

Those points aside, a better strategy might to explain what you want
to calculate, with enough about your data and some example data for
people to follow.
Nick
njcoxstata@gmail.com


On 3 October 2013 10:18, Paul Balcombe
<paul.balcombe@postgrad.manchester.ac.uk> wrote:
> I have a timeseries data set and I want to generate a number of variables that are conditional on each other and their previous values, so I want to create a value for the set of variables at each time period in my data. I thought I should use a forvalues command, but this is new to me and I have so far been unsuccessful: invalid syntax. below is the command I wish to make:
>
> forvalues datetime= ‘tc(19aug2012 00:00:00)’ (‘tc(00:05:00)’) ‘tc(18aug2013 23:00:00)’ {
>                 replace seen=seen[_n-1] if seen==. & seen3[_n-1]<seen[_n-1]
>                 replace segaspow=segaspow[_n-1] if seen==. & seen3[_n-1]<seen[_n-1]
>                 replace seen2=seen2[_n-1] if seen==. & seen3[_n-1]<seen[_n-1]
>                 replace seen3=seen2+seen3[_n-1] if seen==. & seen3[_n-1]<seen[_n-1]
> }
>
> I may be describing the datetime functions incorrectly.
> Thanks,
> Paul
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