Forum Discussion
PREVIOUSMONTH
You have to read the fine print here to understand how PREVIOUSMONTH (and similar functions) work:
"This function returns all dates from the previous month, using the first date in the column used as input. For example, if the first date in the dates argument refers to June 10, 2009, this function returns all dates for the month of May, 2009."
So, mainly you have to use this in a "context aware way". Here is the example from the page:
Example
The following sample formula creates a calculated field that calculates the 'previous month sales' for the Internet sales.
To see how this works, create a PivotTable and add the fields, CalendarYear and MonthNumberOfYear, to the Row Labels area of the PivotTable. Then add a calculated field, named Previous Month Sales, using the formula defined in the code section, to the Values area of the PivotTable.
=CALCULATE(SUM(InternetSales_USD[SalesAmount_USD]), PREVIOUSMONTH('DateTime'[DateKey]))
My understanding of how this works is that the row labels are context filters that filter the 'DateTime' table to that specific year and month, so in the context of the pivot table (matrix) for each particular row, the 'DateTime' table has been filtered such that when you pass PREVIOUSMONTH the 'DateTime'[DateKey] column, you are only passing in the dates for a specific year and month, like June 2009. Thus, PREVIOUSMONTH sees that and goes and grabs the dates for the previous month and passes those back as filters to the CALCULATE function. I don't think that the page really explains it all very well, but that is my understanding of how it is supposed to work.
Here is a good article on context in DAX formulas that might help as well.
You have to read the fine print here to understand how PREVIOUSMONTH (and similar functions) work:
"This function returns all dates from the previous month, using the first date in the column used as input. For example, if the first date in the dates argument refers to June 10, 2009, this function returns all dates for the month of May, 2009."
So, mainly you have to use this in a "context aware way". Here is the example from the page:
Example
The following sample formula creates a calculated field that calculates the 'previous month sales' for the Internet sales.
To see how this works, create a PivotTable and add the fields, CalendarYear and MonthNumberOfYear, to the Row Labels area of the PivotTable. Then add a calculated field, named Previous Month Sales, using the formula defined in the code section, to the Values area of the PivotTable.
=CALCULATE(SUM(InternetSales_USD[SalesAmount_USD]), PREVIOUSMONTH('DateTime'[DateKey]))
My understanding of how this works is that the row labels are context filters that filter the 'DateTime' table to that specific year and month, so in the context of the pivot table (matrix) for each particular row, the 'DateTime' table has been filtered such that when you pass PREVIOUSMONTH the 'DateTime'[DateKey] column, you are only passing in the dates for a specific year and month, like June 2009. Thus, PREVIOUSMONTH sees that and goes and grabs the dates for the previous month and passes those back as filters to the CALCULATE function. I don't think that the page really explains it all very well, but that is my understanding of how it is supposed to work.
Here is a good article on context in DAX formulas that might help as well.
Hi smoupre,
yes, PREVIOUSMONTH always returns all dates from the previous month (in the current filter context). If you add the "Days" field to the rows of your PivotTable, your formula returns the SalesAmount for ALL days of the previous month and not only for the SAME day of the previous month. As long as you stay with MonthNumberOfYear in rows, you are fine...
If you use
= CALCULATE (
SUM ( InternetSales_USD[SalesAmount_USD] ),
DATEADD ( 'DateTime'[DateKey], -1, MONTH )
)
you'll get the correct SalesAmount on a daily and monthly basis
To prevent the incorrect result from showing in the subtotal row for CalendarYear and in the Grand Total, you can use
= IF (
HASONEVALUE ( 'DateTime'[MonthNumberOfYear] ),
CALCULATE (
SUM ( InternetSales_USD[SalesAmount_USD] ),
DATEADD ( 'DateTime'[DateKey], -1, MONTH )
),
BLANK ()
)
Best regards
Dominik Petri
- Got it! Let's say I want to do same period last year, How do I make the visual always open to YTD filter? Now I understand the formula, but I can't set the filter to make the formula work without actually using the filters along the side. So for example, every day when I open my dashboard, I want to see YTD sales & sales of same period LY. Make sense?
PBI filters do not allow programmatic criteria. You can't set the filter on a date to < TODAY().
You have to set a literal value in a filter.
This makes it seems like an awful problem to solve, but it's actually trivial to do at a level before the presentation layer.
Create a field in your date dimension for CurrentYTD. Then you can filter on [CurrentYTD] = True.
Power Query offers a very useful function for adding this field to any date dimension Date.IsInYearToDate(). As you refresh your model daily, this field will always be up to date, and you never have to change your filter criteria.
OK... that was awesome ... thanks! Next issue ... My view is showing all current YTD values and then I want to show SamePeriodLastYear values alongside as a comparison. But once I use the YTD page level filter, then all previous dates are no longer available to use the same period LY function??
