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From |
"Steinar Fossedal" <[email protected]> |

To |
<[email protected]> |

Subject |
st: RE: RE: Calculating the changing proportion of a population with a certain property over time |

Date |
Mon, 12 Dec 2005 23:13:36 +0100 |

```
Thanks Nick,
however I suspect the -egen- command you mention would only calculate
generate the means for observations with a record at the specific time
step. If I could make it calculate the mean using the lowest time step
equal to or above the step we're trying to calculate, it would solve my
problem though (the property is sticky, it's a one-way ticket). I know
MS Excel has options for this using -vlookup/hlookup-, but the dataset
won't fit in Excel.
-lowess- could be usable if it smoothed over time intervals instead of
records, but I can't see how to make it do so.
The typical structure of my data is something like
ID Time prop
1 1 0
1 2 0
1 4 0
1 5 0
1 6 1
1 60 1
2 1 0
2 2 0
2 3 1
2 48 1
Notice the jumps in timespan. Smoothing within a window of records
instead of time would produce quite different results - unless, of
course, I could somehow add the extra records (from 10 through 59 for ID
1 in the example). This would solve the problems using -egen- too. From
the example above, the result I'm looking for would be something like
Time Sumprop
1 0
2 0
3 1
4 1
5 1
6 2
...
60 2
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Nick Cox
Sent: 12. desember 2005 20:01
To: [email protected]
Subject: st: RE: Calculating the changing proportion of a population
with a certain property over time
Create a variable
gen is_one = prop == 1
and
lowess is_one time
egen mean_is_one = mean(is_one), by(time)
etc.
Nick
[email protected]
Steinar Fossedal
> I have a survival time dataset with customer information, and
> I want to
> create a plot which shows the proportion of the population with a
> certain nominal property as it changes over time. Thus I would like to
> calculate the number of customers with the property at each time, and
> divide it to the number of total customers (or customers with another
> interesting property). Since there is not a record at each time t for
> every customer, I can't simply calculate it from the records directly.
> (- count if prop==1 & time==9 - would miss customers which got the
> property at time 8)
>
> Any suggestions as to how I can do this? I played with the idea to
> create records for all time intervals, but I can't seem to
> find an easy
> way to duplicate observations either.
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```

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