Power bi box and whisker: filter with an if statement

Question

MWE set up:

1) From the Power Bi visual website: https://app.powerbi.com/visuals/ there is a custom download "Box and Whisker (Jan Pieter)"

2) Download sample.

3) create new measure with dax formula:

Distinct count score = if(distinctCOUNT(Courses[Score]) > 4, average(Courses[Score]), Blank())

4) Add a Stacked column chart with Course as the axis and the newly created 'Distinct count score' as the Value and get the following:

5) compare this graph to the Box and Whisker provided by Power BI:

Here is my problem. I only want to show values in the Box and Whisker where the Distinct Count of Scores is greater than 4 -- So I only want Physics to show up (like the stacked column chart above).

So if I try the solution working with the stacked bar chart using the Dax formula. I get the following--nothing shows up:

And this is what I want to happen:

Question:

Is there a way in Power BI run and distinct count statement within a Box and Whisker chart to only show data with > 4 distinct values (or any if statement)?

I want it to be formula based, I cannot just 'visual filter' items I do not want.

Possible answer:

I thought about going to the source code to try and 'throw in' a if statement. But I went to the developers git hub: https://github.com/liprec -- I couldn't find the repo for this visual.

Answer 1

Basically this is due to the way the box and whisker chart is working. The visuals needs a dataset to calculate the values (mean, median, etc.) and use those values to show the box and whisker.

So in your case you need to create a measure that is on the same level as the scores (because those values are needed) and is only available. See the screenshot for a visual explanation of the needed measure.

I created the measure with the follow DAX measure:

Filter Score = IF(CALCULATE(DISTINCTCOUNT(Courses[Score]), ALLEXCEPT(Courses, Courses[Course]))>4, MIN(Courses[Score]), BLANK())

The Boolean expression of the IF statement calculates the distinct scores per course via a CALCULATE expression and the ALLEXCEPT filter option to ignore everything but the course value. And the TRUE part returns the score which needs to be aggregated, so the MIN and the FALSE part return a BLANK() value so is can be ignored.

When you add the new measure and create a BW chart it will only show 'Physics' course results.

If you need more help, please let me know here or via email.

-JP

BTW: I just updated my PowerBI visual GitHub repository (https://github.com/liprec/PowerBI-custom-visuals) and added my box and whisker chart and my hierarchy slicer to it in the folder oldAPI.

Answer 2

The crux of your problem, as far as I can tell, is that you want to filter visuals to courses that have a particular number of distinct values. Which visual you want to use is almost irrelevant (though it was helpful to have a sample Power BI workbook to follow along with).

The way I'd approach this (and not saying this is the best or only way)

Step 1

Create a new Course dimension table, with one row for each unique course. In the sample workbook, you can click 'Enter Data' and manually type in the data.

Course
------
English
Math
Physics

Step 2

Next, create a calculated column in the new table and calculate the distinct count for each course. This isn't a measure - it's a column in your table, that uses the Distinct Count calculation from your question.

Distinct Count = CALCULATE(DISTINCTCOUNT(Courses[Score]), SUMMARIZE('Courses','Courses'[Course])) 

The SUMMARIZE works like a GROUP BY. In essence, creating one row per course with a distinct count of scores.

Step 3

Use this new attribute as a filter on your visual. You can then dynamically alter the number of distinct values as you feel like (4, 3, 2).

I know this isn't quite as good as typing a formula into the visual filter field, though in practice it's still formula driven. The formula is just on an underlying table.

Why so complex?

The reason you have to do this for the Box & Whiskers visual, whereas your 'Distinct Count score' measure works so well, is that on the column chart, you are displaying a single value (the average score). The Box & Whiskers chart, by contrast, is plotting every individual score.

In fact, if you removed the 'Course' from the axis of your column chart, the value changes as it adds back in the courses you filtered out. (The reason for this is that, if no course is on your axis, your formula calculates the distinct count of all the courses, which is 7). Likewise, if you were to filter your column chart to a particular session, your column chart would go blank (since in any given session, no course has more than 4 distinct values).

The technique I've described above fixes those problems, because it filters out the courses Math & English from the get-go. It doesn't matter if you've filtered to a single session, or not filtered by course at all. English & Math will always be excluded as long as their distinct count is below the value you specify.

Hope this helps.