From: "Nick Cox" <[email protected]>
Reply-To: [email protected]
To: <[email protected]>
Subject: st: RE: grouping by time window
Date: Mon, 13 Jun 2005 14:35:13 +0100
I am not sure this is determinate on the
criteria given. In particular, if you
start a first window at the first
observation and then use the rule that
no window can be more than a year long,
then the windows so produced do not
necessarily coincide with the set
of disjoint windows that maximise the
number of products within each, if
indeed there is a unique set so
defined.
A quite different comment -- and here
you may well have a rationale not presented --
is that seems a rather arbitrary way
to reduce these data.
Nick
[email protected]
Andre pierre
> I would like to create groups of observations with at least 2
> products
> invented within 365 days (not a civil year), by firm and
> industry code.
>
> obs; Firm; ic; date
> 1; 1; A; 31 dec 02
> 2; 1; A; 2 Apr 03
> 3; 1; A; 12 dec 03
> 4; 1; A; 5 jan 04
> 5; 1; A; 4 may 04
> 6; 1; B; 4 may 04
> 7; 2; A; 1 jan 01
> .
> .
> .
>
>
> In this example, observations 1 to 3 and 4 to 5 would correspond to a
> "group", as the products are invented by the same firm, in
> the same industry
> code within 365 days. The groups have to be "successive", and not
> "overlapping".
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