I am facing a problem right now that I can’t find the answer to in any online research.
I have a calculated measure as follows…
top_selected_tier:=CALCULATE(
min(Table1[waterfall_tier]),
ALLSELECTED(Table1)
)
…that shows the correct value in the measure pane, after slicing the [waterfall_tier] field (using either slicers or filter dropdowns).
However, when I reference that measure in a calculated column…
[test_top_tier]=[top_selected_tier]
… I get a different value. It essentially returns the lowest value in the table, irrespective of which set of filters/slicers are applied.
What I need to test for is whether the field [waterfall_tier] at the row level matches the currently lowest value for [top_selected_tier] that is selected via slicers as reported in the measure pane.
Similarly, in another calculated column I am trying to do a sum of all “filled” requests in the table for a given date, and I don’t know how to construct the formula to only sum the selected values (via slicer/filter dropdown). Instead this formula sums all the values for that day, irrespective of the set of filters/slicers applied.
[all_filled]=CALCULATE(
sum([requests]),
FILTER(ALLEXCEPT(Table1,Table1[request type],Table1[date]),
[request type]="filled"
)
)
In effect I need the formula to return an ALLEXCEPT on the ALLSELECTED subset of table… if that makes sense?
Please note the features of the CALCULATE:
New filter context is added.
The function transform existing row contexts into an equivalent filter context.
The preceding simultaneous occurrence.
Calculated columns are not dynamic, that's why you are getting a fixed value. (see this article)
One important concept that you need to remember about calculated columns is that they are computed during the database processing and then stored in the model.
This means that the column value is evaluated only once, in the beginning, when there are no filters yet, and therefore the "ALLSELECTED" dataset is the whole table.
In PowerBI (sadly) you cannot create a dynamic column.
Related
I have a tricky situation in Microsoft Power BI, and DAX language:
I am developing a new Calculated Column called Status_CC in a table called Customers; we refer to this formally as - Customers[Status_CC].
This calculated column (Customers[Status_CC]) has a number of conditions in its derivation, I am using SWITCH statement to develop it.
i.e.
Status_CC = SWITCH(
TRUE(),
.........
)
One of the conditions to develop the this Customers[Status_CC] calculated column is: Customers[HireDate] > [BonusDate].
The intersting part is, HireDate is an existing column in the Customers table.
However, [BonusDate] is a measure; this measure is developed using another table called WorkHistory.
A column (called PayCategory) from the WorkHistory table acts as a slicer in the report visual. The PayCategory column determines the value of the [BonusDate] measure.
I am using the DAX function ALLSELECTED on the slicer - the WorkHistory table's PayCategory column, to develop the [BonusDate] measure.
My question is, will the calculated column Customers[Status_CC] work correctly, if it depends on the [BonusDate] measure, which in turn depends on another table WorkHistory, which feeds PayCategory that acts as a slicer ?
I don't see any syntax error in Customers[Status_CC], but not sure whether the numbers are right.
My final report visual in Power BI Report View has:
-several columns from the Customers table, including the calculated column Customers[Status_CC]
-a slicer with PayCategory from the WorkHistory table that dictates the value of the [BonusDate] measure.
Any advice, please?
Measures used in calculated columns are calculated at model refresh time for each row. The row context is transformed to a filter context during the calculation of the measure, and is the only active filter for the measure calculation. So no report filters or slicers would be active at that point.
Note for that non-measure expressions the row context is not transformed to a filter context, so you would see a global total on each row, unless you explicitly use calculate which always changes the row context into a filter context.
I have a table with 2 measures - One and Two. Both uses CALCULATE and have a filter. There's also a slicer. While Two rightfully ignores slicer's filter context, One doesn't.
'Years'[Year] is a Whole number.
One = CALCULATE(SUM(Years[Sales Amount]),FILTER(Years, 'Years'[Year] = 2010))
Two = CALCULATE(SUM(Years[Sales Amount]),'Years'[Year] = 2010)
What am I missing (in my learning)? I understand Microsoft recommends to NOT use FILTER as filter argument. I'm merely trying to get a grip on the way it works.
There are some tricky details on CALCULATE that produce different results. I’ll show the differences and provide examples below.
Measure One
One = CALCULATE(SUM(Years[Sales Amount]),FILTER(Years, 'Years'[Year] = 2010))
First, remember that every language calculates from the most internal to the most external function.
It means that Power BI will first calculate the function FILTER, which will return a table that contains only the year 2010. Only after that Power BI will perform CALCULATE.
A tricky part here: If there is a filter in the 2nd parameter, the CALCULATE can ignore the slicer (more details on measure two). However, there is no filter on the 2nd parameter, there is only a table! (previously calculated, which contains only year 2010 now).
Since there is no filter, CALCULATE applies the context filter (the slicer in your example) excluding anything before 2013.
Given that, no rows match the filters for Measure One and the result will be blank (if the slicer is set to 2013-2018, of course).
Measure Two
Two = CALCULATE(SUM(Years[Sales Amount]),'Years'[Year] = 2010)
Measure Two do have a filter expression: 'Years'[Year] = 2010
When filter expressions are provided, the CALCULATE function changes the filter context (which contains slicers or filter on page etc.) to evaluate the expression.
For each filter expression, there are two potential outcomes in CALCULATE:
Outcome A. If the columns are already in the filter context, the existing filters will be overwritten by the parameter in the CALCULATE expression. I.e., does not matter the slicer (or filter on this page or on all pages…)
That is the case for your measure two!
Since you are using 'Years'[Year] in both the CALCULATE expression and the slicer, the context filter will be overwritten by the filter in the CALCULATE expression. I mean, the result is ignoring the slicer/filter context and you will find "3" as the result.
Outcome B. If the columns aren't in the filter context, then new filters will be added to the filter context to evaluate the expression. In other words, it will consider both the slicer/filter context and the filter expression in CALCULATE.
To exemplify this behavior, I have created a new measure:
ThreeSalesFilter = CALCULATE(SUM(Years[Sales Amount]), 'Years'[Sales Amount]=3)
It keeps the exact same row as measure two, right? The Year=2010 is the same row Sales Amount=3.
However, the result of this measure is blank and not 3. Quite interesting!
Again, it happens because CALCULATE is using 'Years'[Sales Amount] but the slicer/filter context is using 'Years'[Year] – another column. Therefore the CALCULATE filter "joins" the filter context; do not overwrite it.
Below, the reproduction of the dashboard including my third variable.
If you need more details or clarifications, please let me know in the comments and I'll edit here.
You are getting different behaviors because of the way that the CALCULATE function works with filter context; you are passing two different types of arguments into the calculate function.
In measure one you are passing a table filter expression. It takes the table created by the FILTER function, and then applies the filter context given by the slicer. Table filter expressions do not override the existing filters on any columns.
In measure two you are passing a Boolean filter expression as the second argument. It overrides the filter context since they both filter based on the year column, therefore ignoring the slicer.
MS best practices do caution against using FILTER as a filter argument, but they do also mention examples of several times where it is appropriate.
I try to create a table like yours
also create the two measures which build on the dashboard
So, I think the values displayed by One and TWO are not the same as the DAX syntax. But your One is BLANK that the possible reason is that One caught the filter condition on the right side of your way, while TWO caught the value of the table on the left, I guess it is because it's not the same.
For a table (having 2 rows and 3 columns namely City1,Price1 & Units1) in power bi, I created a new column (named 'salesColumn') and a new measure (named 'salesMeasure) with the below DAX queries
salesColumn = SUMX('Table', 'Table'[Price1] * 'Table'[Units1])
salesMeasure = SUMX('Table', 'Table'[Price1] * 'Table'[Units1])
This resulted in the following visual:
As seen above, formula for both the column & measure are same but still they give different results. While salesColumn gives 6572 (12*175 + 18*229) in both rows, salesMeasure gives the row wise product. Can anyone please let me know why the behaviour is different in the two cases while we are using the same formula ? SUMX is a function to which we are passing the same arguments. If we are passing same arguments to a function, the function should behave in the same manner, but it is not so. Is there any hidden argument being passed to SUMX ? Can anyone please explain what is happening here & possibly paste some relevant links to understand this better ?
This Two calculation should give you different output, the reason is that the SaleColumn are calculated only once at refresh time (The DAX expression defined for a calculated column operates in the context of the current row across that table.) --> you calculate a value for all rows (look at the summary from salesMeasure), while SaleMeasure is dynamic.
Even if they look similar, there is a big difference between
calculated columns and measures. The value of a calculated column is
computed during data refresh and uses the current row as a context; it
does not depend on user interaction in the report. A measure operates
on aggregations of data defined by the current context, which depends
on the filter applied in the report – such as slicer, rows, and
columns selection in a pivot table, or axes and filters applied to a
chart.
https://www.sqlbi.com/articles/calculated-columns-and-measures-in-dax/
Power BI allows to add calculated field and measure to table. Both create new column and allow me to add DAX formula.
When to use calculated field vs measure in Power BI?
The most important difference is that calculated columns are calculated once when the dataset is loaded. Their value does not change later, i.e. it is not affected by slicers for example. Measures are dynamic. They are calculated whenever necessary, thus they will respond to slicers in the report.
I would recommend to read this article - Measure vs Calculated Column: The Mysterious Question? Not!
Rule of thumb: If you want to use it in a filter or a slicer, put it in a column. Otherwise, you can create it as a measure.
Link: https://learn.microsoft.com/en-gb/learn/modules/dax-power-bi-add-measures/5-compare-calculated-columns-measures
Regarding similarities between calculated columns and measures, both are:
Calculations that you can add to your data model.
Defined by using a DAX formula.
Referenced in DAX formulas by enclosing their names within square brackets.
The areas where calculated columns and measures differ include:
Purpose - Calculated columns extend a table with a new column, while measures define how to summarize model data.
Evaluation - Calculated columns are evaluated by using row context at data refresh time, while measures are evaluated by using filter context at query time.
Storage - Calculated columns (in Import storage mode tables) store a value for each row in the table, but a measure never stores values in the model.
Visual use - Calculated columns (like any column) can be used to filter, group, or summarize (as an implicit measure), whereas measures are designed to summarize.
I'm trying to count days between a date from the column 'completionDate' and today
The table name is 'Incidents (2)'
I have a simuler table called 'incidents' here it's working.
The code:
DaysClosed = DATEDIFF('Incidents (2)'[completionDate].[Dag];TODAY();DAY)
The error i get:
'A single value for variaton 'Dag' for column 'completionDate' in table 'Incidents (2)' cannot be determined. This can happen when a measure formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result.'
The error you get strongly depends on how you are evaluating your formula, that's why it might work on another table but not on this one. As #JBfreefolks pointed out correctly you are specifying a column where a scalar value is expected. That can work depending on the context you are evaluating your formula over (assuming it is a measure).
For instance, imagine a data-set with 100 rows equally divided into four categories A,B,C,D. When you create a table visual with a row for each category, each row will have 25 underlying records that will be used in any calculation added to this row (either a measure or an aggregate of any value). This means that when using a formula like datediff with a column reference, it will get 25 values for it's second argument where it expects one.
There are several ways to solve the problem depending on your desired result.
Use a measure like MAX like #JBfreefolks suggested to make sure that a single value is selected from multiple values. The measure will still be calculated over a group of records but will summarize it by taking the maximum date.
Make sure the visual you are using has something like an ID in there so it doesn't group, it displays row context. Any measure added to this visual will evaluate in row context as well.
Use a calculated column instead. They are always evaluated in row context first and their values can be aggregated in a visual later on. When using TODAY() , you probably need to refresh your report at least every day to keep the column up to date.
A more complicated way is to use an iterator like SUMX() or AVERAGEX() to force row context evaluation inside of a measure.
Good to see you solved it already, still posting as it might be helpful to others.
'Incidents (2)'[completionDate].[Dag] referencing a colomn. It is in your computation returning a table (multiple date in the evaluation context) instade of a scalar needed in DATEDIFF calculation.
You need to leverage to be sure that 'Incidents (2)'[completionDate].[Dag] is rturning a scalar value. To do that you can leverage rowcontext and then also formula like Max.