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Re: st: Duration data- count number of spells with ref to current spell
From
Nick Cox <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: Duration data- count number of spells with ref to current spell
Date
Mon, 26 Aug 2013 21:37:14 +0100
The cumulative or running sum is given by -sum()-. For a toy dataset
apply this separately.
. bysort id : gen cumact = sum(activity)
. l
+------------------------+
| id activity cumact |
|------------------------|
1. | 1 1 1 |
2. | 1 3 4 |
3. | 1 5 9 |
4. | 1 7 16 |
5. | 1 9 25 |
|------------------------|
6. | 2 2 2 |
7. | 2 4 6 |
8. | 2 6 12 |
9. | 2 8 20 |
+------------------------+
The activity before any event is
by id : gen before = cumact[_n-1]
The activity after any event is
by id : gen after = cumact[_N] - cumact
In your case, you will want to sort by time, but the main idea should
carry over.
Nick
[email protected]
On 26 August 2013 20:51, Sriram Narayanamoorthy <[email protected]> wrote:
> Hello everyone,
>
> This question is on data generation when working with a
> discrete-duration datasets. The dataset I have includes all the
> activities undertaken by individuals in a 24 hour period. The day is
> divided into 48 half-hour intervals. The start interval of a spell is
> denoted by a variable called eventStart. The activity type is denoted
> by the variable eventType.
>
> The task of counting the number of activities of a particular type
> undertaken in a day by the person is quite straightforward using egen.
>
> However, I want to generate a variable as the number of activities of
> a particular type undertaken by the individual before/after the
> current activity. How do I add the "Before" and "After" dimension to
> my variable? To be sure, I want to compare the eventStart of my
> current record with all other records for that person and count the
> number of records of a particular eventType only if eventStart is less
> than (for Before) or greater than (for After) the current start
> period.
>
> Any thoughts? Is there a mata approach to this? Thanks much for the inputs!
>
> Thanks,
> -Sriram
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