Date:         Wed, 9 Jan 2008 16:40:31 -0800
Reply-To:     sylia <sylia.chen@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         sylia <sylia.chen@GMAIL.COM>
Organization: http://groups.google.com
Subject:      how to count the unique frequency?
Comments: To: sas-l@uga.edu
Content-Type: text/plain; charset=ISO-8859-1

The sample dataset is below:

ID      year    quarter month   buy     channel multichannel
1       1998    1       2       1       N       0
1       1998    2       5       1       S       1
1       1998    3                               2
1       1998    4       12      1       N       2
1       1999    1       1       1       M       2
1       1999    2                               3
1       1999    3       7       1       R       3
1       1999    3       9       1       R       4
1       1999    4       11      1       W       4

=================================
I need to count the multichannel. The multichannel is defined as the
number of unique multichannel until the current quarter. For 1998,
quarter 1, the multichannel is 0 since it's the first quarter and has
no previous record. 1998, quarter 2, the multichannel is 1. And 1998,
quarter 3 is 2. 1998, quarter 4, the multichannel is also 2 since N
has appeared before and should not be counted again. Follow this role,
1999, quarter 4, multichannel is 4 instead of 5 because the current
quarter purchase is not included.

Please tell me how to write the sas proc code. I thought about it all
day and couldn't figure an way out.

Thank you very much!