Date:         Thu, 18 May 2006 12:08:08 -0400
Reply-To:     Richard Ristow <wrristow@mindspring.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Richard Ristow <wrristow@mindspring.com>
Subject:      Re: Classifying products by date of launch and mechanism of Action
Comments: To: Sibusiso Moyo <smoyo@targetrx.com>
In-Reply-To:  <B2A95412067E5C4CBA09E2E92D81BF290506CB16@TRX-V01.targetrx. com>
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At 09:55 AM 5/17/2006, Sibusiso Moyo wrote:

As an aside, in your test data, most dates are in the form 'Aug-84';
i.e., the launch date is month and year. A number (9, I think) are in
the form '2-May'; those, I think, don't give the year, and so can't be
used in the calculation.

You ask,
>I [want to classify] a product into three categories: Leader, Follower
>and Copy within a MARKET [and ACTION]. The code has to meet the
>following criteria:
>o       If there is a single product [for a combination of MARKET and]
>ACTION, then it is a Leader
>o       If there is more than one product [for a combination of MARKET
>and]  ACTION, then the one with the earliest date of launch is the
>leader, the rest are FOLLOWERS

So far, so good. I've changed your definitions to what I think you
actually meant.

Now, for COPY,

>o       COPY is a subcategory of FOLLOWER where product maker
>(company) appears more than once within an ACTION on different dates

So, a product is a COPY if there's another, earlier product FROM THE
SAME COMPANY within [a combination of MARKET and] ACTION

>o       COPY also exists if LEADER shows up on a later date with a
>product for the same action.

This one, I plain don't understand. LEADER is the earliest product for
a combination of MARKET and ACTION, so this criterion should never be
met.

Further, different companies can make the same product, introduced on
the same date. But one of the companies may have introduced an earlier
product within the same combination of MARKET and ACTION. Is this
product a COPY, or not? Or does it need two classifications, as
FOLLOWER for one of the companies and COPY for the other?