# Rolling N months

This document demonstrates creating Flags in the script to calculate Rolling N Months data.

Same thing can be achieved in various ways using set analysis, rangesum fuction,Accumulation on front end. But if Month or MonthYear field is used in chart or any selection is done on Month or MonthYear , it will be difficult to achieve the Rolling calculation using above methods and sometimes expression becomes quite complex.

So it is better to create the Flags from back end in a master calender itself.

This method will create the flag for rolling months which can then be used in front end for selection.This provides better flexibility for users to select the Rolling periods of his choice or this flags can be used in set analysis.

In the application I have created the dummy data to link to the calender.

// Load min and max Date from Fact

MaxDate:

num(min(FieldValue('Date', recno()))) as MinDate

AUTOGENERATE FieldValueCount('Date');

let vMaxDate= Peek('MaxDate',0,'MaxDate');

let vMinDate= Peek('MinDate',0,'MaxDate');

// Generate Dates using min and max date

Cal:

MonthName(Date) as MonthYear;

AutoGenerate(1)

While \$(vMinDate)+IterNo()-1<=\$(vMaxDate);

MaxMonthYear:

AUTOGENERATE FieldValueCount('MonthYear');

//  Variable used to restrict MonthYear to <=current month while looping

LET vMaxMonthYear = monthname(Peek('MaxMonthYear',0,'MaxMonthYear'));

// Define Rolling N in Inline table. 1 is the default value for current month

RollMonth:

RollMonth

1

2,

3,

6,

12 ];

Calender:

junk ];

for i=1 to FieldValueCount('RollMonth')

LET vRollMonth= FieldValue('RollMonth',\$(i));

Concatenate(Calender)

MonthYear,

Rolling_Months,

month(Rolling_Months) as Month,

Year(Rolling_Months) as Year,

if(Flag='Rolling1','CurrentMonth',Flag) as Rolling_Flag

where Rolling_Months<=Date#('\$(vMaxMonthYear)','MMM YYYY');

MonthYear,

monthname(MonthYear,IterNo()-1) as Rolling_Months,

'Rolling'&\$(vRollMonth) as Flag

Resident Cal

While IterNo()-1<=\$(vRollMonth)-1 ;

NEXT

DROP Tables Cal,MaxMonthYear,RollMonth;

DROP Field junk;

Pease find the attached QVW file