Monday, August 6, 2018

Data Science in Power BI: Clustering

Today, we're going to talk about Clustering within Power BI.  If you haven't read the previous posts in this series, Introduction and Getting Started with R Scripts, they may provide some useful context.  You can find the files from this post in our GitHub Repository.  Let's move on to the core of this post, Clustering in Power BI.

Clustering is a statistical process by which we group records or observations into categories based on how similar they are to one another.
This is very easy to visualize in two dimensions.  We can see that clustering can be used to determine that there are three groups of observations, known as clusters, in our data.  As we add more dimensions, it becomes difficult, or even impossible, to visualize.  This is where clustering algorithms can help.  You can read more about Clustering here.

Fortunately, the Power BI Marketplace has a pre-built "Clustering" visual that uses R scripts on the back-end.  Let's check it out!

We start by opening the "Customer Profitability Sample PBIX" we downloaded in the previous post.  In case you haven't read that post, you can find the file here.
Import From Marketplace
Then, we navigate to the "Visualizations" pane and select "... -> Import From Marketplace".
Power BI Marketplace
This takes us to the "Power BI Marketplace".  Here, we can look at all of the custom visuals created by Microsoft and members of the community.
Power BI Marketplace (Cluster)
If we search for "cluster", we can add the "Clustering" custom visual by clicking the "Add" button.  This will add this custom visual as an option in our Power BI Report.
We can see that the "Clustering" custom visual has been added to the list.  Let's make a new page in the report and add an empty "Clustering" chart.
Enable Script Visuals
We were prompted to enable script visuals.  This is necessary when we utilize R scripts or custom visuals that utilize them.  If you get some type of error here, you may need to read the previous post to ensure your R environment in Power BI is correctly configured.
Can't Display This Visual
During this process, we also stumbled across this error.  The "Clustering" chart tries to load a number of R packages.  However, these R packages need to be installed on the machine in order for this to work.  Fortunately, it's pretty simple to install packages using RStudio.
Install Packages
We kept installing packages until we completed the list.  There is one package, Redmonder, that we could not install through RStudio.  Instead, we had to download the package from here and manually copy it to the R package directory.  In our case, this is
 Once we completed that, we faced our next challenge.  This custom visual does not allow us to use measures.  This means that basic questions like "How many clusters of customers exist based on Total Revenue and Total Labor Costs?" become more complex to solve.  Fortunately, it's not too difficult to turn the measures into calculated columns.  We do this by creating a new table in Power BI.
New Table
We start by selecting the "New Table" button in the "Modeling" tab at the top of the screen.
Customer Summary
Then, we use the following code to create a table "CustomerSummary".  This table contains one record for each Customer Name, along with the Total Revenue and Total Labor Costs associated to that Customer.


CustomerSummary = 
,"Total Revenue", SUM( 'Fact'[Revenue] )
,"Total Labor Costs", SUM( 'Fact'[Labor Costs Variable] )


You can read more about the SUMMARIZE() function here if you are interested.
Total Revenue and Total Labor Costs by Customer Name
Finally, we can create our Clustering chart by adding [Total Revenue] and [Total Labor Costs] to the "Values" shelf and [Name] to the "Data Point Labels" shelf.  The resulting chart is less than inspiring.  "Cluster 2" at the top-right of the chart contains two outlying points, leaving "Cluster 1" to contain the rest of the dataset.  The issue here is that K-Means Clustering is not robust against outliers.  You can more about K-Means Clustering here.

In order to make a more interesting set of clusters, we need a way to reduce the influence of these outliers.  One approach is to rescale the data so that extremely large observations aren't quite so large.  Two common functions to handle this are logarithm and square root.  Let's alter our code to take the square root of [Total Revenue] and [Total Labor Costs].


CustomerSummary = 
,"Total Revenue (Square Root)", SQRT( SUM( 'Fact'[Revenue] ) )
,"Total Labor Costs (Square Root)", SQRT( SUM( 'Fact'[Labor Costs Variable] ) )


Since we altered the field names, we also need to recreate our chart to contain the [Total Labor Costs (Square Root)] and [Total Revenue (Square Root] fields in the "Values" shelf.
Total Revenue (Square Root) and Total Labor Costs (Square Root) by Customer Name
We can see that we now have a more interesting set of clusters.  The outliers are still present, but not nearly as dominant.  This custom visual has quite a few more interesting options.  We encourage you to play around with it to create some visuals that would not be possible in standard Power BI.

Hopefully, this post opened your eyes to the Data Science possibilities in Power BI.  The power of custom R scripts has created a new world of potential, just waiting to be unleashed.  Stay tuned for the next post where we'll be talking about Time Series Decomposition.  Thanks for reading.  We hope you found this informative.

Brad Llewellyn
Senior Analytics Associate - Data Science
Syntelli Solutions

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