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Author: Kevin Feasel

Calculating Color Contrast

Published 2020-08-26 by Kevin Feasel

Meagan Longoria has a new Power BI report for us:

Color contrast (as calculated in the WCAG 2.1 success criteria) is dependent on luminance. Luminance is the relative brightness of any point in a color space, normalized to 0 for darkest black and 1 for lightest white. In order to calculate color contrast you must first get the luminance of each color.

As an example, I have colors #F3F2F1 and #007E97. In this hex notation, often explained as #RRGGBB, the first two digits represent red, the second two digits are green, and the last two digits are blue. Each two digits is a value that represents the decimal numbers 0 to 255 in hexadecimal notation. The same red, green, and blue values can be represented in decimal notation as integers, and this is what is used to calculate luminance. #F3F2F1 is RGB(243, 242, 241), and #007E97 is RGB(0,126,151).

Read the whole thing, check out the report, and test those color contrast values.

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Displaying Map Routes with Power BI

Published 2020-08-26 by Kevin Feasel

Chris Webb lays out map routes:

In last week’s post I described the new Power Query M functions for working with Well Known Text objects, and in a post a few weeks ago I showed how you can use the Icon Map custom visual to display Well Known Text data. In this post I’ll show you how you can put all this together to do something really useful: display routes on a map in a Power BI report.

First of all you’ll need to download the latest version of the Icon Map custom visual here, because at the time of writing the version in AppSource doesn’t have the WKT functionality needed. Second, you’ll need a data source with a table of latitudes and longitudes that represent points on a route that you want to plot. I’m going to use the Azure Maps Get Route Directions API as my data source; to keep things simple I’m going to use the Shared Key authentication method for this API, but I’ll explain below why this can be a problem in the real world. To follow the example you’ll need to create an Azure Maps Account in the Azure Portal so you can get your own key.

Read on for an interesting demo.

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Explaining the ROC Plot

Published 2020-08-25 by Kevin Feasel

Nina Zumel takes us through what each element of a ROC curve means:

In our data science teaching, we present the ROC plot (and the area under the curve of the plot, or AUC) as a useful tool for evaluating score-based classifier models, as well as for comparing multiple such models. The ROC is informative and useful, but it’s also perhaps overly concise for a beginner. This leads to a lot of questions from the students: what does the ROC tell us about a model? Why is a bigger AUC better? What does it all mean?

Read on for the answer.

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Creating a Power BI Report in Portrait Mode

Published 2020-08-25 by Kevin Feasel

David Eldersveld controls the horizontal; David Eldersveld controls the vertical:

The default Power BI report layout uses a landscape orientation. While it’s not common to see report pages that use portrait mode, Prathy Kamasani (blog/twitter) has a notable example in Power BI here. Others have tried it as well. It’s used occasionally in other data communities or data-driven journalism. Overall, if you want to guide someone through your analysis by having them scroll like a web page, it may be an option to try.

So what happens if I create a report with a vertical layout in Power BI?

Read on for an example as well as some pros and cons of the idea.

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Managing Azure IoT Digital Twins with Python

Published 2020-08-25 by Kevin Feasel

Paul Hernandez continues a series on digital twins:

As mentioned in my previous post, Azure Digital Twins (ADT) Service is a new way to build next generation IoT solutions. In the first post I show you in a video how to manage ADT instances with the ADT Explorer. In the second post I show how to do mostly the same but using Postman and the ADT Rest API.

ADT has control plane APIs and data plane APIs. The latest is used to manage elements in the ADT instance. In order to use these APIs Microsoft published a .Net (C#) SDK. And SDK is a convenient way to manage instances, since you can easily create applications for your digital twins. If for any reason you prefer to use another language like java, javascript or python, you need to generate your own SDK.

In this post I describe how to autogenerate a Python SDK using the tool Autorest and a swagger file.

Read on to see how you can manage digital twins by generating an SDK.

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Skipping SSIS Package Validation

Published 2020-08-25 by Kevin Feasel

Andy Leonard takes us through a new feature in Visual Studio:

A new feature in version 3.9 of the Visual Studio 2019 SSIS extension is “skip package validation.” I’ve tested the functionality and it works well. Here’s how you set it up:

Click through to see how easy it is to enable. I’d imagine that this would work really well when dealing with dynamic packages where connection details aren’t available until runtime. Waiting for validation to fail to connect to a remote data source (on the UI thread!) was always annoying.

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Estimated I/O Costs and Spills

Published 2020-08-25 by Kevin Feasel

Hugo Kornelis goes deep into the rabbit hole:

Typically, when I look at an operator that does I/O, I expected to see values in both the Estimated CPU Cost and the Estimated I/O Cost. An Index Seek locates specific data in an index. The CPU has to do some work, but most of the cost of this operator is the actual I/O. So when I look at an execution plan and I see an Index Seek that has an Estimated CPU Cost of  0.0001787 and an Estimated I/O Cost of 0.003125 (almost 20 times as much), I am not surprise. That’s an expected ratio.

Conversely, operators that don’t do any I/O should of course be estimated to have a zero I/O cost. And that is indeed the case. Operators such as Nested Loops, Assert, or Row Count Spool will always have an Estimated I/O Cost of zero.

And then there are some operators where the Estimated I/O Cost may or may not be zero.

Hugo then walks us through a case where the optimizer is promising you a bad time if you run the query.

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T-SQL Tuesday 129 Round-Up

Published 2020-08-25 by Kevin Feasel

Tamera Clark wraps up T-SQL Tuesday #129:

Well, I don’t even know what to say, such great ideas and creativeness. The last couple of days I have internally struggled with, as Glenn wrote this ” human malware situation”. Reading all of these posts has made me smile.

Read on for twelve people’s thoughts on this month’s topic, a time capsule for SQL Server professionals.

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Querying Power BI from Visual Studio Code

Published 2020-08-25 by Kevin Feasel

Phil Seamark shows us how to write queries against Power BI using Visual Studio Code:

It’s helpful to understand there are two main client libraries for Analysis Services. A client library is what you can add to any new Visual Studio Code Project to provide objects, methods and functions relevant for the tool you are building.

Make sure you download the NetCore (.Net Core) versions of these libraries when working with Visual Studio Code. There are .Net Framework versions of these libraries that are more suited to use with the full Visual Studio product.

Read on for links to those libraries and a thorough demonstration.

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