Date:         Wed, 12 Dec 2007 16:58:29 -0800
Reply-To:     tanwan <tanwanzang@YAHOO.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         tanwan <tanwanzang@YAHOO.COM>
Organization: http://groups.google.com
Subject:      Re: How to etermine if date is a holiday
Comments: To: sas-l@uga.edu
Content-Type: text/plain; charset=ISO-8859-1

With millions of records, adding an extra variable may not be the most
efficient approach. If you really have to add an extra variable, then
you might want to add a numeric variable [e.g. 1 meaning Holiday and 7
meaning Not holiday].

It depends on what you want to do ultimately. For example, if you just
want to print things, or if u want to split the data, of do an
analysis on purchases made on holidays vs non-holidays, and you have a
format, you may not have to create another variable, leading to
efficiency gains. Again, formats are potentially useful here since you
know all the holidays you want, and they are very few compared to the
365/6 day in a year.

But ultimately it depends on where you are at, and your intended
'destination', and perhaps to a lesser extent, the date ranges in your
data, and the computing resources available to you. Without further
info, I can only 'speculate', but prima facie I would suggest take a
very close look at formats. They are potentially efficient for data
look-up, especially if the data are sorted.