I am looking to build a DAX formula in Power BI that allows me to compare week-to-date (WTD) values for the current year with the corresponding week from the previous year. Specifically , I want to create a measure that calculates the difference in values between the current WTD and the same period last year on a week-by-week basis.
Could someone provide guidance on how to structure this DAX formula to achieve this Year-over-Year (YoY) comparison for WTD values in Power BI? Any insights, examples, or resources would be greatly appreciated. Thank you!
I have been testing different DAX codes to achieve a Year-over-Year (YoY) comparison for week-to-date (WTD) values in Power BI. So far, I have only been successful in calculating Year-to-Date (YTD) and Quarter-to-Date (QTD) values. However, I am struggling to find a solution for WTD comparison between the current year and the previous year on a week-by-week basis.
Could someone provide guidance on how to structure a DAX formula to achieve this YoY comparison for WTD values in Power BI? Any insights, examples, or resources would be greatly appreciated. Thank you!
Power BI doesn't have good week to date functions which is why I love to have offsets in my date table. Do you have a date table? If so, do you have any columns about weeks?
Here's what I would do. Either create offsets in your date table or use this example m code for a new date table. (learn more about offsets here)
let
// configurations start
Today=Date.From(DateTime.LocalNow()), // today's date
FromYear = 2020, // set the start year of the date dimension. dates start from 1st of January of this year
ToYear=2025, // set the end year of the date dimension. dates end at 31st of December of this year
StartofFiscalYear=7, // set the month number that is start of the financial year. example; if fiscal year start is July, value is 7
firstDayofWeek=Day.Monday, // set the week's start day, values: Day.Monday, Day.Sunday....
// configuration end
FromDate=#date(FromYear,1,1),
ToDate=#date(ToYear,12,31),
Source=List.Dates(
FromDate,
Duration.Days(ToDate-FromDate)+1,
#duration(1,0,0,0)
),
#"Converted to Table" = Table.FromList(Source, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
#"Renamed Columns" = Table.RenameColumns(#"Converted to Table",{{"Column1", "Date"}}),
#"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Date", type date}}),
#"Inserted Year" = Table.AddColumn(#"Changed Type", "Year", each Date.Year([Date]), Int64.Type),
#"Inserted Start of Year" = Table.AddColumn(#"Inserted Year", "Start of Year", each Date.StartOfYear([Date]), type date),
#"Inserted End of Year" = Table.AddColumn(#"Inserted Start of Year", "End of Year", each Date.EndOfYear([Date]), type date),
#"Inserted Month" = Table.AddColumn(#"Inserted End of Year", "Month", each Date.Month([Date]), Int64.Type),
#"Inserted Start of Month" = Table.AddColumn(#"Inserted Month", "Start of Month", each Date.StartOfMonth([Date]), type date),
#"Inserted End of Month" = Table.AddColumn(#"Inserted Start of Month", "End of Month", each Date.EndOfMonth([Date]), type date),
#"Inserted Days in Month" = Table.AddColumn(#"Inserted End of Month", "Days in Month", each Date.DaysInMonth([Date]), Int64.Type),
#"Inserted Day" = Table.AddColumn(#"Inserted Days in Month", "Day", each Date.Day([Date]), Int64.Type),
#"Inserted Day Name" = Table.AddColumn(#"Inserted Day", "Day Name", each Date.DayOfWeekName([Date]), type text),
#"Inserted Day of Week" = Table.AddColumn(#"Inserted Day Name", "Day of Week", each Date.DayOfWeek([Date],firstDayofWeek), Int64.Type),
#"Inserted Day of Year" = Table.AddColumn(#"Inserted Day of Week", "Day of Year", each Date.DayOfYear([Date]), Int64.Type),
#"Inserted Month Name" = Table.AddColumn(#"Inserted Day of Year", "Month Name", each Date.MonthName([Date]), type text),
#"Inserted Quarter" = Table.AddColumn(#"Inserted Month Name", "Quarter", each Date.QuarterOfYear([Date]), Int64.Type),
#"Inserted Start of Quarter" = Table.AddColumn(#"Inserted Quarter", "Start of Quarter", each Date.StartOfQuarter([Date]), type date),
#"Inserted End of Quarter" = Table.AddColumn(#"Inserted Start of Quarter", "End of Quarter", each Date.EndOfQuarter([Date]), type date),
#"Inserted Week of Year" = Table.AddColumn(#"Inserted End of Quarter", "Week of Year", each Date.WeekOfYear([Date],firstDayofWeek), Int64.Type),
#"Inserted Week of Month" = Table.AddColumn(#"Inserted Week of Year", "Week of Month", each Date.WeekOfMonth([Date],firstDayofWeek), Int64.Type),
#"Inserted Start of Week" = Table.AddColumn(#"Inserted Week of Month", "Start of Week", each Date.StartOfWeek([Date],firstDayofWeek), type date),
#"Inserted End of Week" = Table.AddColumn(#"Inserted Start of Week", "End of Week", each Date.EndOfWeek([Date],firstDayofWeek), type date),
FiscalMonthBaseIndex=13-StartofFiscalYear,
adjustedFiscalMonthBaseIndex=if(FiscalMonthBaseIndex>=12 or FiscalMonthBaseIndex<0) then 0 else FiscalMonthBaseIndex,
#"Added Custom" = Table.AddColumn(#"Inserted End of Week", "FiscalBaseDate", each Date.AddMonths([Date],adjustedFiscalMonthBaseIndex)),
#"Changed Type1" = Table.TransformColumnTypes(#"Added Custom",{{"FiscalBaseDate", type date}}),
#"Inserted Year1" = Table.AddColumn(#"Changed Type1", "Year.1", each Date.Year([FiscalBaseDate]), Int64.Type),
#"Renamed Columns1" = Table.RenameColumns(#"Inserted Year1",{{"Year.1", "Fiscal Year"}}),
#"Inserted Quarter1" = Table.AddColumn(#"Renamed Columns1", "Quarter.1", each Date.QuarterOfYear([FiscalBaseDate]), Int64.Type),
#"Renamed Columns2" = Table.RenameColumns(#"Inserted Quarter1",{{"Quarter.1", "Fiscal Quarter"}}),
#"Inserted Month1" = Table.AddColumn(#"Renamed Columns2", "Month.1", each Date.Month([FiscalBaseDate]), Int64.Type),
#"Renamed Columns3" = Table.RenameColumns(#"Inserted Month1",{{"Month.1", "Fiscal Month"}}),
#"Removed Columns" = Table.RemoveColumns(#"Renamed Columns3",{"FiscalBaseDate"}),
#"Inserted Age" = Table.AddColumn(#"Removed Columns", "Age", each [Date]-Today, type duration),
#"Extracted Days" = Table.TransformColumns(#"Inserted Age",{{"Age", Duration.Days, Int64.Type}}),
#"Renamed Columns4" = Table.RenameColumns(#"Extracted Days",{{"Age", "Day Offset"}}),
#"Added Custom1" = Table.AddColumn(#"Renamed Columns4", "Month Offset", each (([Year]-Date.Year(Today))*12)
+([Month]-Date.Month(Today))),
#"Changed Type2" = Table.TransformColumnTypes(#"Added Custom1",{{"Month Offset", Int64.Type}}),
#"Added Custom2" = Table.AddColumn(#"Changed Type2", "Year Offset", each [Year]-Date.Year(Today)),
#"Changed Type3" = Table.TransformColumnTypes(#"Added Custom2",{{"Year Offset", Int64.Type}}),
#"Added Custom3" = Table.AddColumn(#"Changed Type3", "Quarter Offset", each (([Year]-Date.Year(Today))*4)
+([Quarter]-Date.QuarterOfYear(Today))),
#"Changed Type4" = Table.TransformColumnTypes(#"Added Custom3",{{"Quarter Offset", Int64.Type}}),
#"Added Custom4" = Table.AddColumn(#"Changed Type4", "Year-Month", each Date.ToText([Date],"MMM yyyy")),
#"Add Week Offset" = Table.AddColumn(#"Added Custom4", "Week Offset", each ( Number.From( Date.StartOfWeek( [Date], Day.Sunday) )- Number.From( Date.StartOfWeek( Today, Day.Sunday ) ) ) / 7, Int64.Type),
#"Added Custom5" = Table.AddColumn(#"Add Week Offset", "Year-Month Code", each Date.ToText([Date],"yyyyMM")),
#"Changed Type5" = Table.TransformColumnTypes(#"Added Custom5",{{"Year-Month", type text}, {"Year-Month Code", Int64.Type}})
in
#"Changed Type5"
After you have your week offset column, create new measures like
Last Week Sum = CALCULATE(SUM([your value here]),Date[Week Offset] = 0)
Prior Year Last Week Sumh= CALCULATE(SUM([your value here]),Date[Week Offset] = -53)
You could then find the difference between the two measures for your variance. This might seem like a lot if you don't have a date table, but it is really a best practice to have a date table you can use in all of your reporting.
It's common to publish this table in dataflows so it can be easily consumed with any report.