The reason you need it wide is to do statistical analysis; for instance proc logisitic code would be:
model disease=snp1 snp2 snp3;
Virtually all SAS STAT procedures expect data to be wide rather than long; thus the need to be able to transpose back and forth.
----- Original Message -----
From: Ian Whitlock
Sent: Wednesday, September 10, 2008 11:40 AM
Subject: Re: KEEP DROP array variables
Summary: Deleting obs and variables - efficiency and bugs
email@example.com asked a question involving 6651 one byte character
variables. He wanted to subset rows to those where some variable was
"U", and he wanted to keep only those columns that had some value "U"
It is hard for me to imagine how such a data set can be of much use,