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Category: DAX

Minimizing Callback Counts in SUMX()

Published 2023-10-24 by Kevin Feasel

Marco Russo and Alberto Ferrari speed things up a bit:

Pushing calculations down to the VertiPaq storage engine is always a good practice. Sometimes this is not feasible. However, carefully analyzing the aggregated expression can lead to optimization ideas that produce excellent query plans.

DAX developers should not be scared of iterators. Their performance is great as long as the expression computed during the iteration can be pushed down to the VertiPaq storage engine. 

Read on to understand what they mean by callback and the enormous performance cost you’ll want to avoid.

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Conditional Formatting in Power BI with Field Parameters and Calculation Groups

Published 2023-10-10 by Kevin Feasel

Marco Russo and Alberto Ferrari perform some formatting:

If you want to build a report where the user can choose what measure to show, you have two features available in Power BI: field parameters and calculation groups. There are pros and cons to either technique – however, we are not about to talk about those. We narrow our scenario down to a specific requirement: we want to change the color of the value depending on the measure selected.

For example, suppose we let users choose between Sales Amount, Margin, or Total Cost. In that case, we might provide visual feedback about the measure selected through different colors: black for Sales Amount, green for Margin, and red for Total Cost.

Click through for that example, though I will say that the color choices are hard to differentiate if you have protanopia and even more difficult if you have deuteranopia, so about 2% of the male population would struggle with interpreting this measure. People with protanomaly and deuteranomaly (about 6% of men) wouldn’t have too much difficulty with this particular color pairing.

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Dynamic Highlighting of Data Points Based on Slicer Selection

Published 2023-09-25 by Kevin Feasel

Nikola Ilic shines a light on the data:

To quickly explain: when a user selects, for example, Contoso in the slicer, the Contoso bar should be highlighted by using a different color. As much as this sounds like a very basic and common business request, there is no straightforward solution in Power BI (or, at least, I’m not aware of it:))

However, the client’s wish is (almost) always our command – so, let’s see how this feature can be implemented with a little bit of data model tweaking and leveraging some DAX code.

Spoilers: there is a solution, though it does involve quite a few steps.

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Using DAX to Find Products Missing Sales

Published 2023-09-25 by Kevin Feasel

Marco Russo and Alberto Ferrari observe the dog that didn’t bark:

What products did not sell in a specific area, store, or time period? This may be an important analysis for several businesses. There are multiple ways to obtain the desired result. Some specific implementations might be needed because of the user or model requirements, whereas developers can choose any formula in several cases. Or you might just find a solution on the web and blindly implement it without questioning whether there is a better way to achieve what you want.

It turns out that different formulas perform very differently. Choosing the right one in your scenario can make a slow report fast. This article analyzes the performance of different formulations of one same algorithm. 

It’s interesting to see the performance profile here: most are reasonably close together, although you can still get a 2x gain from using the fastest approach versus the second-slowest. And then there’s the slowpoke.

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Controlling Power BI Chart Ranges with DAX

Published 2023-09-12 by Kevin Feasel

Marco Russo and Alberto Ferrrari control the horizontal, Marco Russo and Alberto Ferrari control the vertical:

DAX is a powerful tool in the hands of a Power BI developer. Using simple DAX formulas, you can not only compute interesting metrics but also customize the behavior of Power BI visuals. In this article, we use DAX to control the range of charts to obtain more coherent visualizations.

Read on to see how.

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First Impressions of DAX Optimizer

Published 2023-09-07 by Kevin Feasel

Nikola Ilic takes a look:

A few months ago, while scrolling through posts on social media, one of them immediately grabbed my attention! It was about a new tool, called DAX Optimizer, which promised to identify and remove performance bottlenecks in your DAX formulas. For all of us dealing with optimizing Power BI reports on a day-to-day basis, that was a huge promise (and one I was impatiently waiting to see in action).

One important note is that this is not a free tool, as Nikola mentions. Read on for more thoughts about how it works, what it picks up, and whether it’s a good fit for your environment given the price.

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A Currency Conversion Pattern for DAX

Published 2023-09-05 by Kevin Feasel

Teo Lachev pulls out the money clip:

Currency conversion is a common requirement, such as when implementing analytics on top of ERP sales data recorded in multiple currencies. The most flexible approach is to allow the user to select a currency and perform the conversion at runtime, ideally by centralizing the conversion code in Power BI calculation groups. However, this approach has several shortcomings:

Read on for those shortcomings, as well as an approach Teo has to improve things.

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Comparing GROUP BY and SUMMARIZE in DAX

Published 2023-08-17 by Kevin Feasel

Marco Russo and Alberto Ferrari make a comparison:

DAX offers a rich set of functions, some of which overlap in their functionalities. Among the many, two functions perform grouping: SUMMARIZE and GROUPBY. These are not the only two: SUMMARIZECOLUMNS and GROUPCROSSAPPLY perform similar operations. However, the article is about SUMMARIZE and GROUPBY, as the other functions have many more functionalities, so a comparison would be unfair.

To make a long story short: GROUPBY should be used to group by local columns, columns created on the fly by DAX functions. SUMMARIZE should be used to group by model and query columns. Be mindful that both functions support both scenarios: both functions can group by model and local columns. However, using the wrong function translates into a strong decrease in performance.

Read on for a detailed explanation.

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Range-Based Groupings in Power BI

Published 2023-08-04 by Kevin Feasel

Gilbert Quevauvilliers pulls back the curtain:

I was once again working with the grouping feature in Power BI Desktop.

This time I had a lot of values that I wanted to put into multiple groups. I also did not want to select the individual values (I have previously shown this in my blog post Creating a group with all values (Even if not in the data) in Power BI)

It is amazing that sometimes it takes me a while to fully understand how to use some features in Power BI and today was one of those days!

Click through to see what Gilbert learned and how you can use that information to group by ranges instead of individual values.

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Filtering Calculation Items in a Slicer

Published 2023-07-18 by Kevin Feasel

Marco Russo and Alberto Ferrari do some slicing and filtering:

Slicers with too many values might be inconvenient for users, as they must search for the desired selection among too many lines. In such cases, a common solution is to build a hierarchy and use slicers with multiple columns inside, or multiple slicers, each with one column. However, this solution works only in structures with a natural hierarchy, like continents and countries. Indeed, each country belongs to only one continent so the hierarchy can be easily created with a new column.

If the hierarchy is non-natural, the relationship between the parent and the children is many-to-many, requiring a specific type of relationship. 

Click through to see what that relationship looks like and how you can build it.

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