Tuesday, October 24, 2023

How to create and filter list of Dates using Power Query in Power BI

How to create and filter list of Dates using Power M-Query in Power BI
Scenario:
We want to create a List of Dates of Current Month and then Filter out the Dates of Week 2 and Week 4, using Power M-Query.
Next we want to use these Filtered List of Dates into another Date Table as a Filter based on the Parameter value.
We can achieve this Scenario, using the following following M-Query.
ListOfDates :

let
    vTodayDate = Date.From(DateTime.LocalNow()),
    vStartDate = Date.StartOfMonth(vTodayDate),
    vEndDate = Date.EndOfMonth(vTodayDate),
    
// Create List of Dates based on Current Month (Eg; October-2023) //
    vDatesList =     
    List.Dates(vStartDate, Duration.Days(vEndDate-vStartDate)+1, #duration(1,0,0,0)),
    
// Filter Week3,Week4 Dates //
    vFilterLsit = List.Select(vDatesList, each List.Contains ({2,4},Date.WeekOfMonth(_)))  
    
    /*
    vYear = Date.Year(vTodayDate),
    vQtr = Date.QuarterOfYear(vTodayDate),
    vMonth = Date.Month(vTodayDate),
    vMonthName = Date.MonthName(vTodayDate),
    vMonthWkNo = Date.WeekOfMonth(vTodayDate),
    vMonthWeek = "Week " & Number.ToText(vMonthWkNo)
    vPrevDay = Date.AddDays(vTodayDate,-1),
    vPrevWeek = Date.AddWeeks(vTodayDate,-1),
    // Start of Week: 0 for Sunday as Default; 1 for Monday //
    vPrevWkStartDt = Date.StartOfWeek(vPrevWeek)
    */

in
    vFilterLsit

Result:

-------------------------------------------------------------------------------------------------------------------
Next we we can use the above Filtered List of Dates (Week 3, Week 4) as Filter into another Date Table (DimCalendar), based on a Parameter Value.


Conditions:
If the Parameter "pDateFilterFlag" = 1 then Filter the Week 2 and Week 4 Dates.
If the Parameter "pDateFilterFlag" = 0 then Exclude the Week 2 and Week 4 Dates

DimCalendar:

let
/* Create the List of Dates based on Current Month */
vStartDate = Date.StartOfMonth(Date.From(DateTime.LocalNow())),
vEndDate = Date.EndOfMonth(Date.From(DateTime.LocalNow())),
DatesList = 
    List.Dates(vStartDate, Duration.Days(vEndDate-vStartDate)+1, #duration(1,0,0,0)),
DatesTable = 
    Table.FromList(DatesList, Splitter.SplitByNothing(), null, null, ExtraValues.Error),

DimDate = 
    Table.RenameColumns(DatesTable,{{"Column1", "DimDate"}}),
DimYear = 
    Table.AddColumn(DimDate, "DimYear", each Date.Year([DimDate])),
DimQtr = Table.AddColumn(DimYear, 
           "Qtr", each "Q" & Number.ToText(Date.QuarterOfYear([DimDate]))),
MonthNo = 
            Table.AddColumn(DimQtr, "MonthNo", each Date.Month([DimDate])),

// Filter Dates based on the List "ListOfDates" //
FilterWeekDates
            Table.SelectRows(MonthNo, each List.Contains (ListOfDates,[DimDate])),

/ Exclude Dates based on the List "ListOfDates" //
ExcludeWeekDates
            Table.SelectRows(MonthNo, each not List.Contains (ListOfDates,[DimDate])),

// Filter or exclude Week 2 and 4 Dates based on the Parameter (pDateFilterFlag) value. //
vResult = if pDateFilterFlag = 1 then FilterWeekDates else ExcludeWeekDates
in
    vResult

Result:

Thanks, TAMATAM

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