Creating Fundamental Metrics definition in Omniture Insight

I have been confused for quite some time now over how the fundamental metrics in Omniture Insight /Visual Sciences (VS) are defined. Well recently I found out that the definitions are rather simple.
The keyword that I am going to focus on here is “Shift” which is used in a lot of fundamental Insight Definitions.

The syntax of using this keyword to create dimension is something like this:


Shift(Dim,Level,Group,N)  and this is how it is explained in the VS documentation :
“Defines a dimension having the same elements as the dimension Dim. The eth element of the dimension level relates to the same element of the new dimension as the element of Dim related to by the e+Nth  element  of Level provided  that the eth and e+Nth element of level relate to the same element of the dimension group.”

Confused??

Let’s look at an example to make things clear.

Definition of metric Entries: The number of sessions that entered the site on each page. This metric is evaluated over the Page Dimension
Formula : Page_Views[not shift (None,Page_View,Session,-1) = “ ”]
Now what this definition does is consider the number of Page Views for all the sessions in which the previous page was not within the same website .

Bounce Rate :  (Bounce Rate is basically all sessions having only single page views )/All Sessions
Formula : Page_Views[not shift(None,Page_View,Session,1) and not shift(None,Page_View,Session,-1)]
Again what the formula signifies is all those sessions for which the previous page (-1 in the formula) and next page (1 in the formula) are not in the website.

Hope this helps!!