What is Deneb Power BI?

If you've ever felt boxed-in by the standard visuals in Power BI, you're not alone. While the built-in charts are great for everyday reporting, sometimes you need to create something truly specific, highly customized, or just plain different. This article explains how Deneb, a free custom visual for Power BI, gives you the toolkit to build almost any data visualization you can imagine directly inside your reports.

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What is Deneb in Power BI?

Deneb is a custom visual that acts as a canvas for creating your own visualizations using the powerful and declarative languages of Vega-Lite and Vega. Think of it as a certified "sandbox" that you add to your Power BI report. Inside this sandbox, you are no longer limited by the formatting panes and menus of traditional Power BI visuals. Instead, you write a simple text-based specification (in JSON format) describing exactly what your chart should look like, and Deneb renders it for you.

It was created by Daniel Marsh-Patrick and opens up a universe of charting possibilities that were previously only accessible to web developers. With Deneb, you can build everything from advanced statistical plots to beautiful, bespoke branded charts, all integrated with the interactivity of your Power BI model.

Why Go Beyond Standard Power BI Visuals?

Power BI's native visuals are fantastic for quickly building standard reports. Bar charts, line charts, and pie charts are just a few clicks away. So why would you add the complexity of writing code for a chart?

The answer lies in the limitations you eventually encounter:

• Limited Customization: Have you ever tried to add custom annotations, layer different chart types in a very specific way, or control every single aesthetic element like spacing, fonts, and axis lines? The standard formatting pane can be restrictive and, at times, frustrating.
• Need for Non-Standard Charts: What if you need a box plot, a violin plot, a density plot, or a calendar heatmap? While some of these are available as separate custom visuals, Deneb lets you build them yourself and combine them with other elements, giving you more control over the final product.
• Composition Complexity: Creating composite visuals in Power BI often involves layering different charts on top of each other, which can be clunky and difficult to maintain. Deneb allows you to define multiple layers within a single, cohesive visual specification. For example, you can plot bars, a line, and individual data points on the same axis within one Deneb visual.

Deneb overcomes these hurdles by giving you a direct line to the visual's anatomy. Instead of clicking through menus, you describe the chart you want, and it gets built exactly to your specifications.

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The Magic Behind Deneb: Understanding Vega and Vega-Lite

Deneb itself doesn't invent a new way to chart, it provides an interface to two existing, well-established visualization 'grammars': Vega-Lite and Vega. A "grammar of graphics" is a formal system for describing the components of a statistical graphic.

Instead of thinking "I need to draw a bar chart," you think, "I need to map my product categories to the X-axis, my sales figures to the Y-axis, use rectangular 'marks' for the data, and color them blue." This descriptive approach is what makes them so powerful.

Vega-Lite: The Perfect Starting Point

For most Power BI users, Vega-Lite is where the journey begins. It's a higher-level language that simplifies the process of creating common charts. With Vega-Lite, you don't have to specify every detail. You describe the essentials, and it intelligently figures out the rest, like axes and legends.

A Vega-Lite specification is a JSON file that typically contains:

• data: Defines the data source (in Deneb, this is passed in from Power BI).
• mark: The type of visual shape you want to represent your data (e.g., "bar", "line", "point", "area").
• encoding: The heart of the spec. This is where you map your data fields to visual properties (channels) like the x-axis, y-axis, color, size, shape, and tooltips.

Vega: For Maximum Control

Vega is the lower-level language that Vega-Lite is built on. It gives you explicit, fine-grained control over every single pixel of your visualization. While Vega-Lite is great for rapid development and standard charts, Vega is what you use when you need intricate interactivity, custom legends, or a truly unique and complex design.

For most business reporting needs, Vega-Lite is more than sufficient. You can think of the learning path as mastering Vega-Lite first, and only turning to Vega if you hit a hard limit on what you can achieve.

How to Start Using Deneb: A Step-by-Step Guide

Let's walk through creating your very first Deneb visual. The process is surprisingly straightforward.

Step 1: Get Deneb from AppSource

You can't use Deneb if you haven't added it to your Power BI Desktop file. In the Visualizations pane, click the three dots (...) and select 'Get more visuals'. In the AppSource marketplace, search for "Deneb" and click 'Add'.

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Step 2: Add Data to the Visual

Once added, the Deneb icon (a constellation) will appear in your Visualizations pane. Click it to add the visual to your report canvas.

Next, you need to provide data. This is a crucial step. Drag the data fields you want to use for your visualization from the Data pane into the Values field of the Deneb visual. Power BI aggregates this data and then passes the resulting table into the Deneb environment. Don't worry about summarization for now, just add the columns you need.

Step 3: Launch the Visual Editor

With data added, the Deneb visual will prompt you to 'Create' your visual. Clicking this will launch the Deneb Visual Editor in a new window. Here you can choose between Vega-Lite and Vega. We'll stick with Vega-Lite.

Step 4: Create Your First Specification (A Simple Bar Chart)

The editor presents a code pane on the left and a live preview pane on the right. You can start with a template or a blank slate. Let's use a simple template to get started.

Let's say we dragged a 'Product Category' field and a 'Sales' measure into the Values field. The Visual Editor provides boilerplate code for a basic bar chart. Here's a slightly modified version you can paste into the code pane. Note how the "field" names match the columns we added.

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "data": { "name": "dataset" },
  "mark": "bar",
  "encoding": {
    "y": {
      "field": "Product Category",
      "type": "nominal",
      "axis": { "title": "Category" }
    },
    "x": {
      "field": "Sales",
      "type": "quantitative",
      "axis": { "title": "Total Sales" }
    }
  }
}

Let's break this down:

• "mark": "bar" tells Deneb to use rectangular bars.
• "y": { ... } maps our "Product Category" field to the Y-axis. The type "nominal" means it's a categorical variable.
• "x": { ... } maps our "Sales" measure to the X-axis. The type "quantitative" means it's a numerical variable that can be measured.

As you type, the chart in the preview pane updates instantly. Once you're happy, click 'Back to report', and your Deneb creation will appear on the Power BI report canvas, ready to interact with other visuals via filters and slicers.

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Step 5: Customizing and Expanding

Now, let's make a small tweak. We want to color the bars by 'Product Category' as well. We simply add a "color" channel to our encoding section:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "data": { "name": "dataset" },
  "mark": "bar",
  "encoding": {
    "y": {
      "field": "Product Category",
      "type": "nominal",
      "axis": { "title": "Category" }
    },
    "x": {
      "field": "Sales",
      "type": "quantitative",
      "axis": { "title": "Total Sales" }
    },
    "color": {
      "field": "Product Category",
      "type": "nominal",
      "legend": null
    }
  }
}

By adding that color block, Vega-Lite automatically assigns different colors to each category. We set "legend": null because having a legend is redundant when the Y-axis already labels the categories.

Inspiration and Key Tips

Getting started is one thing, but mastering Deneb is a journey. Here are a few tips to help you along the way:

• Browse the Vega-Lite Example Gallery: Stuck for ideas or syntax? The official Vega-Lite Example Gallery is your best friend. It has hundreds of examples with copy-pasteable code for nearly any chart type you can imagine.
• Use the "Repair and Format" Tool: A misplaced comma in JSON can break everything. The Deneb editor includes a handy tool to automatically fix common formatting errors. Use it often.
• Inspect Your Dataset: Sometimes a chart fails because the data isn't in the format you expect. Inside the Deneb editor, there is a data tab that shows you the exact table that Power BI passed to the visual. This is invaluable for debugging.
• Start Simple: Don't try to build a stunning, multi-layered masterpiece on your first try. Build a simple bar chart. Then a scatter plot. Add color. Add tooltips. Building your skills incrementally will make the process much more enjoyable.

Final Thoughts

Deneb brings a new level of power and flexibility to an already amazing BI tool. By integrating the Vega and Vega-Lite grammars, it gives data professionals the ability to break free from visual constraints and build the exact charts and graphics their data stories require, without ever leaving Power BI.

While Deneb is fantastic for crafting custom visuals inside Power BI, sometimes the bigger challenge is just getting all your marketing and sales data into one place for a consolidated view. The time spent downloading CSVs from different platforms, wrestling with formulas, and trying to build multi-channel reports is a huge drain on productivity. At Graphed, we solve this by letting you connect your sources like Google Analytics, Shopify, Facebook Ads, and Salesforce in seconds. From there, you can ask for the dashboard you need in plain English - no JSON required. It's an effortless way to create unified, real-time reports so you can focus on insights instead of manual reporting.