KB38400: How to compare metric values by quarter in MicroStrategy Developer

In some business scenarios, it is required to compare the metric value with previous quarter's. 
The technical note as below provides a method with using MovingSum() function and basic math operation. 
 
KB5504: How to create a derived metric that shows data from the previous row in MicroStrategy SQL Generation Engine
 
Another way to achieve this is using Lag() function. The Lag function is useful to display a set of metric values in an order determined by another metric or attribute on the report. It helps to compare metric values side-by-side. It is defined as
 
Sample Code/Error
Lag <BreakBy, SortBy> (Argument, Offset, DefaultValue)

• BreakBy is the attribute indicating where the calculation restarts.
• SortBy is the attribute or metric by which the data is sorted.
• Argument is an attribute or metric representing a list of values. It is common to use a metric for Argument.
• Offset specifies the offset from the current row to display information for.
• DefaultValue is the value displayed for any entries that do not have any data due to the offset. Usually enter Null or 0 as default value.

 
EXAMPLE:

• Create a blank report in Strategy Tutorial project
• Insert 2 attributes, "Year" and "Month," and 1 metric, "Cost"
• Run the report, as shown below:
   
  

• Then insert a derived metric called "Quarter Lag Cost" with the following definition into the report.
  
  Sample Code/Error
  
  Lag<BreakBy={Year}, SortBy= (Month) >(Cost, 3.0, 0.0)
  
  
    
  
• Run the report and the newly created metric return with one quater lag metric compared with the "Cost" metric, which is the expected result, as shown below: