Implementing the D3 General Update Pattern into a Qlik Sense Extension

Animation in data visualization is a relatively new area that we still don’t know much about. Like any visual component of a visualization, animations used in the wrong way can be unnecessarily flashy and distracting. However, there is evidence that animations can also add value to visualizations when used appropriately.

In this interactive example, Mike Bostock demonstrates the concept of object constancy:

a graphical element that represents a particular data point…can be tracked visually through the transition. This lessens the cognitive burden by using preattentive processing of motion rather than sequential scanning of labels.

Animation therefore can help users track changes in the data. When filtering, this can help the user discern what changes their filters caused, as opposed to having to reset their bearings on a newly appearing chart. When data in a chart is filtered, there are three possible events that can happen: data elements either update with new properties, exit because they were filtered out of the data set, or enter because they are filtered in to the data set. These are the main events we handle in typical Qlik Sense extensions. For more on animation possibilities, check out https://www.youtube.com/watch?v=vLk7mlAtEXI#t=54

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Your Axis Doesn’t Always Have to Start at Zero

Recently, Justin Fox of Harvard Business Review shared a chart about law school enrollment that he found interesting:

The chart shows how law school enrollment has seen a relatively drastic decline in the last 3 years. You may have noticed that the chart’s y-axis doesn’t start at 0. This design decision caused a bit of an outrage amongst what are now being called “Y-Axis-Zero Fundamentalists”.

Justin shares a lot of the feedback and discussion around this point in his post The Rise of the Y-Axis-Zero Fundamentalists.

The discussion around this point is pretty thorough but I want to add my two cents.

Line charts aren’t just for displaying quantities. They are also used to examine changes in quantities. Sometimes, the change in quantity in relation to the entire size of the quantity is not as important as visualizing the direction and magnitudes of the changes in relation to each other. The chart Justin showcased is a perfect example of this type of analysis. It is probably not important to the average reader that law school enrollment was at ~38,000 in 1974, ~52,000 in 2010, and ~40,000 in 2013. What is important is that the change from 2010 to 2013 was significantly large and fast when compared to the historical trend of enrollment numbers. This analysis comes from comparing the slopes and positions to each other, not from comparing the distance of each point to a zero-based axis.

The exact same chart can be viewed with a zero-axis thanks to a slight variation. By changing the metric being plotted, we get:

Law School Enrollment

Is this chart now valid because the axis has a 0 next to it at the baseline? One could argue that each point is now quantified by it’s distance from the axis. That isn’t the point of this visualization however. The average reader probably does not want to quantify the % change since 1974. The metric also doesn’t provide any means to derive the nominals, a metric that is more real to a reader and easier to interpret.

The original chart’s trade-off of using a non-zero axis with nominal amounts in order to focus on relative changes while retaining a link to the nominal source data so that exact quantities can be derived is valid. The distance of each point to the axis is not visually defined like in a bar chart, so the implication that the distance is equal to the size of the value is not there. Scatter plots use the same positional method of encoding each data point, but I have never heard anyone say that scatterplot axes should start at zero.

In most cases, a zero-based axis makes sense, but it ultimately depends on the data and visualization used. If you are tracking the trend in revenue of a multi-billion dollar company with a line chart for example, you probably won’t learn much if you start the axis at 0.

-Speros

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New senseUtils feature: filterPanel



I’ve added a new component to senseUtils called filterPanel. filterPanel allows a user to define a list of fields in a Qlik Sense application. The object will then generate all of the list objects, retrieve the data from the Qlik Sense server, and build or update the existing filterPanel UI. The panel can be created in an existing element on a webpage.

The panel features badges for the # of selections and collapsible filters by default. These settings can be easily changed with the .badges() and .autoCollapse() methods.

CSS is used for the collapsing behavior as well as the styling. The base css file (filter-panel.css) can be used as a starting point for applying custom styling to the panel. Alternatively, the filterPanel could just be used to create the list objects and keep track of their values. This is possible with the .fields() method, which returns a list of the current fields in the panel as well as attribute like the number selected, the total number of elements, and all of the values of the filter.

Documentation for the panel’s use is in the README of the senseUtils’ repository. An example use, taken from the repository:

app; // assume a Qlik Sense app object exists in this variable

var filterPanel = senseUtils.filterPanel()                      // creates a new filterPanel
                            .app(app)                           // sets the app for panel to pull from
                            .container("#filter_container")     // sets an element with id "#filter_container" as the parent
                            .addFields(["Region","Country"]);   // adds the fields Region and Country to the panel

filterPanel.badges(false); // disables badges

filterPanel.removeField("Region") // removes the Region filter from the panel

The live demo above also uses Bootstrap’s CSS. This helps with some of the text centering, but is not necessary for the panel to function.

-Speros

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How to Destroy a Hypercube

The Qlik Sense Workbench API gives us an easy way to create hypercubes from the browser on a webpage. With these hypercubes, we can create custom visualizations on the web that are driven by dynamic Qlik Sense data. However, one method that is not covered in the Workbench API is removing hypercubes once they have been created. When a hypercube is created, it will continue to process the data on the server and send it back to the browser as long as a user has their current session open. This can cause performance issues in single-page applications that use different cubes in different views.

For example, imagine you built a single-page application with a Dashboard view and a Details view. When you initialize your Dashboard view, you may create some hypercubes for the visualizations on that view. Users may navigate to the Details view next, which also initializes its own set of hypercubes. However, your hypercubes from the previous view will remain active. They will continue to utilize resources on the server, send data back to your browser, and execute their callback functions. This will lead to performance problems as you add views; the server will try to send all of the data across the views back to your browser at once.

A solution to this problem is to destroy cubes. While this is not possible with the Workbench API, the Engine API does give us a methodology for doing this. I’ve recently started a library of JavaScript functions called senseUtils that contains easy to use code for destroying hypercubes. However, this post will explain the details behind how to remove a cube, as well as provide an example of how to incorporate the method in practice manually as opposed to with the library. At the end, I’ll show how the library code can be used instead.
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lasso.js, a D3 plugin for custom drawn brushing

Inspired by Qlik Sense’s lasso tool, I’ve built a lasso tool for D3 that accomplishes similar functionality.

The lasso takes in a d3 selection of elements that are lasso-eligible and allows a user to draw a custom path around those elements. Elements are tagged based on whether they are inside or outside the loops. Custom functions can be defined to do things with these elements, such as style them:

lasso screenshot

The lasso code and documentation is available on GitHub.

View a live example with a scatterplot.

-Speros

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Shakespeare’s Work Emails

From McSweeney’s:

There are more things in heaven and earth, Horatio,
Than will fit in our engagement strategy.

Hath ye spied that client feedback? It is an email
Told by an idiot, full of sound and fury,
Signifying nothing.

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Introducing senseUtils, a JavaScript library for Qlik Sense web development

After building a few mashups with the new Qlik Sense APIs, I ran into problems that required me to do complex coding around the APIs. These problems may arise again so it made sense to write boiler plate code with the APIs to tackle them in the future. I’ve stored these first few functions into a JavaScript library called senseUtils that I hope can become a repository for web development utilities that make Qlik Sense easier to extend.

The library is available on GitHub here.

The first two problems it addresses are:

  1. removing hypercubes after they’ve been created using the Workbench API; this can be useful for situations like a single page application where you need to disconnect from a dashboard view
  2. defining a visualization callback based on multiple cubes. A multicube function is included that can keep track of multiple hypercubes before calling a single callback function. This can be useful for complex visualizations that are dependent on more than one data source

Please feel free to contribute, whether it be by adding your own functions, reporting bugs, or requesting feature enhancements to the library. The latter two items can be entered in the Issues section of the repository.

-Speros

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A scrollable, expandable filter panel for QV 11 – without extensions

A common problem when building QlikView dashboards is where to place listboxes. Often, users want to be able to filter many fields, but there isn’t enough room on the dashboard for all of the listboxes. Some common solutions to this problem are using multiboxes, dynamic listboxes, or creating entire sheets dedicated to housing just filters. I’d like to introduce another out-of-the-box solution to this problem: the filter tree.

Filter Tree

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Co-post with QlikShow: a Qlik Sense Grid Chart extension

I recently collaborated with Patrick Tehubijuluw of the QlikShow blog on a Qlik Sense application. If you haven’t been to Patrick’s blog before, you are really missing out. QlikShow showcases some of Patrick’s excellent examples of UI/UX and data visualization design in QlikView. Patrick also includes tools to help with your own dashboard designs, which I have found very helpful.

The goal of our collaboration was to redesign a QlikView 11 dashboard of Patrick’s for Qlik Sense. While he focused on the challenge of redesigning the dashboard to fit into the Sense framework, I reproduced a chart from QlikView 11 that is not available in Qlik Sense: the grid chart.

screenshot_2

Patrick’s post on designing the dashboard in Qlik Sense can be found here.

The Grid Chart extension, as well as instructions on how to use it, can be found downloaded from GitHub.

UX Improvement: Selections

I want to highlight one portion of the grid chart extension that I believe is an improvement from the QlikView 11 version: the selections. In the original grid chart, selections can be made in two ways:

  1. selecting a value on one axis to select a specific dimension value in a single dimension axis selection
  2. selecting a single bubble to select a specific dimension value in both dimensionsnode selection

However, there is only one way to deselect values in the original grid chart: selecting an already selected value on the axis. This is due to the selection toggle mode. In QlikView and Qlik Sense, there are two possible selection toggle modes:

  • On: when the toggle is on, selecting a value that is already selected in a field removes that selection
  • Off: when the toggle is off, selecting a value that is already selected in a field does nothing

Based on these two options, we can see that the original grid chart has the toggle mode on for the axes selections, but off for the bubble selections. This setup exists to avoid a confusing user experience that can result from having toggle mode enabled on both selections. I will illustrate with a sequence of hypothetical selections.

Let’s assume toggle mode is on for both the axes and the bubbles. The beginning bubble chart state, with no selections:

starting chart

We want to filter the chart by the Dim1 value of B. We click on “B”. Because toggle mode is enabled, and no selections have currently been made, the chart correctly filters to “B”.

B selected

Next, we want to filter by Y, now that we have selected B. There are two options for making this selection: click Y on the Dim2 axis, or click on the giant Y bubble. Let’s click on the giant Y bubble we want, since that is the most natural selection for the user. Because toggle mode is ON for the bubble in this hypothetical scenario, it will have a weird result. It will correctly select “Y” in the Dim2 axis because there are no selections there currently. However, we already have a selection of “B” in Dim1. QlikView will make another selection on “B” in Dim1, and because toggle mode is ON, this selection will actually remove the existing “B” selection. This gives us an odd result based on the user’s behavior of selecting the green bubble above.

Y selected

This result does not make sense based on the intention of the user when clicking a bubble. QlikView 11 solves this problem by turning toggle mode to OFF for the bubbles in the grid chart. This allows the user to always select a single bubble when clicking on it and avoids the scenario above. However, the tradeoff is that selections cannot be removed by clicking the bubbles.

The Qlik Sense Grid Chart improves upon this by incorporating the ability to click on a selected bubble to remove the selection in both dimensions. This functionality results from custom logic used to check the state of selections before determining which action to take whenever a user clicks on a bubble. The end result is a more intuitive and natural selection function for the users.

In a future post, I will provide a tutorial on incorporating selections into Qlik Sense extensions.

-Speros

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Tutorial: How to Build a Qlik Sense Extension with D3

The new Qlik Sense APIs make it extremely simple to build extensions that produce new visualizations. A common source of these visualizations is d3.js, a powerful javascript library for visualizing data.

The following tutorial will show how to create an extension using existing d3 code. The tutorial will go into a bit of detail, so following each step will take some time. However, the steps themselves are simple and without explanation can be completed in under 10 minutes. While the tutorial goes into some granular detail, there are 4 basic steps:

1) Get some d3 code to use

2) Get some test data to use and load it into Qlik Sense

3) Initialize a new extension and set up its properties

4) Insert the d3 code into the extension and modify it to source data from the extension

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