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Category: Visualization

Getting Started with Matplotlib

David Suarez has a primer on the matplotlib library in Python:

Visualization as a tool takes part of the analysis coming from the data scientist in order to extract conclusions from a dataset. In today’s article, we are going to go through the Matplotlib library. Matplotlib is a third-party library for data visualization. It works well in combination with NumPy, SciPy, and Pandas.

Click through for a tutorial.

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Sparklines and Filter Context

Ed Hansberry riffs on the new sparkline functionality in Power BI:

This isn’t a tutorial on how to create sparklines as Microsoft has you covered there. What I want to discuss though is how Sparklines are impacted by the filter context in a visual. First though you need to enable this feature. It is in preview mode at launch, so go to File, Options, Options and Settings, and look for the Preview section. Click Sparklines, then close and restart Power BI Desktop.

In the visual above, I added the “Month” field to the Sparkline settings and that created an additional filter on the visual. Before I added the Sparkline, Year was the only filter affecting the numbers. By adding the month to the sparkline, shown below, it breaks out the Total Net Sales figure by month.

But what if I don’t want the sparkline to be the full range of data. For example, I just want the sparkline to show the last 3 months of the year, so 3 data points, not 12.

Click through to see how it’d look as a measure and what you need to do to make sparklines look right.

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Bullet Charts

Amy Esselman is number one with a bullet:

Our November challenge was inspired by a recent workshop question about bullet graphs. We invited the community to find some data of interest and build their own bullet graph. More than three dozen members tackled this less familiar chart type in a variety of tools, including Excel, Tableau, Python, Illustrator, Datawrapper, PowerBI, and R.

For many challenge participants, this was their first attempt at creating a bullet graph. They discovered, as you may find yourself, that even though bullet graphs are not a typical chart type, they can be powerful in the right situation. 

Click through for examples of bullet charts in action.

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Storytelling with Data Book Review

Camila Henrique has a book review for us:

Hello! As you may have noticed from my Reading List page here, I like to read. Recently, with the new job, I was looking for a book that talked about Data Visualization. While searching, I came across “Storytelling with Data”, and it was not the first time I saw it. After checking a few reviews, I decided to invest my time reading it. Turns out it was a great decision! I liked it so much that I wanted to talk about it here, so here it comes, grab your reading glasses.

This has been on my backlog of books to review, and I agree with Camila that it’s absolutely worth grabbing a copy.

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Re-Making a Line Chart

Alex Velez cleans up a line chart:

When sharing a makeover, typically I’ll show a side-by-side “before” and “after” view. This is a powerful moment for many audiences as they witness the dramatic impact of an effective graph. I share this with you, because until recently if a combination chart was found within my makeovers it represented the “before” state. That’s because most combo charts are hard to read, so I tend to revise them into something simpler—like this makeover.

Today’s article shows the inverse of that process, where, in order to make a visual more informative and easier to understand, I chose to transform the original, a “simple” line chart, into a more “complicated” combination chart. 

This is a good reminder that visuals themselves aren’t necessarily bad (except for the pie chart, which is inherently evil and don’t try to convince me otherwise); it’s all about whether the specific chart makes sense given the story you are trying to tell.

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Graphing Three or More Dimensions

Mike Cisneros takes on a challenge:

When we have three or more dimensions to show, how do you recommend we do it? I worry that my audience might not be able to make sense of it all.

This is a great question. As analysts we are often asked to consider multiple dimensions at once, and investigate complex relationships among these variables. In doing so, we may use visual analyses to explore and find patterns and outliers. The graph types we use to do this tend to be complicated and less intuitive than a simple bar chart or line chart. They might make sense to a trained observer, but to an unfamiliar audience, they’re at best confusing and at worst impenetrable. 

Click through for a few techniques, none of which directly involves 3D graphs, as those are really difficult for humans to understand in most circumstances.

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Voronoi Diagrams with R and x11()

Tomaz Kastrun creates a Voronoi diagram:

Yes. Finally, the Voronoi diagrams with the use of x11() function. This diagram is presentation of a plane that is partitioned every time, a user clicks on the canvas of x11. This plane is partitioned into smaller regions that are close to given set of points.

Partitioning into smaller regions or convex polygons happens in such manner that each polygon contains only one generating point and every point in a given polygon is closer to its generating point than to any other.

I had to take a look out of curiosity, and yes, the x11() function does work on Windows as well.

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Showing Count of Selected Items in a Slicer

Prathy Kamasani wants to track slicer counts:

In one of the projects, I was working on, I received feedback saying it is hard to understand how many items they have selected in a slicer, and it is not the first time I came across this. It is a valid point, especially when you have quite a few items in a slicer, you use a search bar to look for items, you select a couple, but you were not sure how many were selected.

Read on for a rather clever solution to the problem.

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