Graphical Tables – An Alternative to Treemaps

Sean blogged the other day about using a treemap to visualize the drivers of the Australian Inflation. He got inspired to create a treemap by an NYT article that used an interactive version of the following treemap:

NYTTreemap

This chart looks nice on the first view. It makes nice use of muted colors, the shapes look well balanced and certainly the graphic designer did a good job. However, from a data visualization perspective this chart has a couple of flaws.

Ben Shneiderman designed Treemaps to visualize deep directory tree structures.

Ben explained treemaps in an article as:

“Among the growing family of visual analytic tools, treemap are flourishing in organizations that require daily monitoring of complex activities with thousands of products, projects, or salespeople. Tabular reports, bar charts, line graphs, and scattergrams are important tools, but for complex activities where there are numerous sales regions, manufacturing plants, or product lines the hierarchical structures provided by treemaps can be helpful. While tabular displays and spreadsheets can show 30-60 rows at a time on typical displays, the colorful presentations in treemaps can accommodate hundreds or thousands of items in a meaningfully organized display that allows patterns and exceptions to be spotted in seconds.[…] Treemaps are a space-filling approach to showing hierarchies in which the rectangular screen space is divided into regions, and then each region is divided again for each level in the hierarchy.”

The first problem the NYT chart has is that it does not visualize the hierarchy as rectangular areas. The inflation drivers are visualized as asymmetric round shapes. It is difficult to compare the relative size of rectangular shapes but it gets almost impossible for asymmetric shapes. Also does this treemap lack labels for the smaller inflation drivers.

Sean published in his blog post a treemap which does not have the problems mentioned above:image

 

 

 

 

 

 

 

 

 

 

 

Ben designed treemaps to visualize thousands of regions, products, etc ; but the Inflation chart only comprises 20 Inflation Drivers grouped into 7 categories. A simple sorted table would do a better job communicating the numbers as Kaiser Fung from Junk Junks wrote in his post.

Inspired by this post and my comment Sean came up with this graphical sparkline table designed with Excel and MicroCharts.

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This is already quite an improvement on the treemap, as we can see increasing and decreasing inflation trends and sparklines rather than traffic light colors as in the tree map version. Also it is much easier to read for non expert users.

Some minor things we can improve in Sean’s chart are:

  • We can sort the inflation drivers by Weight, to have the most important ones at the top
  • Changing the area to the sparkline puts emphasis on the trend rather than the absolute value of the values (as the area chart does)
  • Inline deviation charts allow us to visualize the MoM and YoY % changes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Applied Gestalt Laws: Table Alignment

Most reports are based on combinations of tabular layouts, so to continue my series about visual design (see my previous post) I will focus on the most common and simple problem to fix: The fundamentals of how to align numbers and text in tables and how to treat their headings.

Here are the rules

  • Right-align a block or column of whole numbers or of whole numbers and text.
  • Left-align a block or column of whole text.
  • Align numbers at the decimal point (or imaginary decimal point).

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Seems obvious really but they are so often rarely applied. A Google image search on “excel table” reveals what most Excel users do

….they simply use what Excel defaults to:

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…or if people are more adventurous often feel that centered columns would somehow looks better:

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…or even worse they apply the Excel Tables styles:

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All those habits make the table more difficult to read. To understand why this is the case let’s use the Gestalt Law of Proximity.

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In the picture above my brain tells me that there are 6 columns of 9 dots in one group. Simply moving the dots of the first row to the left breaks this grouping and differentiates the dots into 2 groups

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This is exactly what happens if you left align column headers on numerical columns: As shown below and the brain does not associate them anymore which is what I want in most cases for headings and numbers.

So Excel Defaults are not right as shown below.

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Right aligning the headers brings them together.

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The grouping still works even if the shapes have a different width but remain either right or left aligned:

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The reason for this is explained by the next Gestalt law of Continuity, the right aligned figures and the left aligned text are perceived as columns

The table below shows this affect with the arrows showing the continuation of the series and the same works with columns of left or right aligned figures or text, we perpetuate the series and perceive the column as one object. Even inserting a row to visually separate the figures and the column headers does not break the grouping…

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….what can be explained by the Gestalt law of Closure.

Hence we perceive the columns of numbers and headers still as a unit even though the headers are placed somewhat apart from the figures.

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If we now disable the Excel grid lines we end up with table which merely relies upon white space and Gestalt laws to format the table providing clear associations: A first class table.

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In western cultures we read text from left to right so it makes a lot of sense to left align text columns but not so for numeric columns. The eye has to search for the decimal point to get to the ten, hundred or thousand digit, this makes comparing numbers quite difficult if not impossible when many numbers are involved.

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Here the Gestalt Law of Continuity can help, simply right aligning brings all tens, hundred, thousand digits on the same virtual line and makes comparison straightforward and simple.

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Unsurprisingly, centering numbers in column causes exactly the same problem as shown below. Another visualization “No No”.

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Interestingly, the same rules apply when we move beyond simple text and numbers to MicroCharts such as sparklines, column charts and bullet graphs. Especially when the sparklines contain m
issing values.

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Right or center alignment leads to severe difficulty comparing values of the same period in different rows in the table.

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If the sparklines have the same amount of data points this is not an issue but in dynamic reports this may not always be the case so its better to be safe than sorry.

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When using visual tables another nice trick to is to introduce an axis to a column chart to aid in the visual alignment and to group periods into blocks through the alternate shadings. The column chart above use a column chart to visualize units sold and an area chart for the other measures. The different shading groups the periods into 6 month units and the column bars aids the visual alignment. So to recap, make it easy for people to read your tables by following how your brain inherently processes information as explained through “Gestalt” laws. Here are the rules again

  • Right-align a block or column of whole numbers or of whole numbers and text.
  • Left-align a block or column of whole text.
  • Align numbers at the decimal point (or imaginary decimal point).

I hope that this article has been useful and I look forward to dealing with other visualization techniques in later posts.

Gestalt Laws, Charts and Tables: The way your brain wants them to be

I get asked by a lot of people how I seem to be able to format my charts and tables so that they look good and still convey the information in the most effective manner. I thought I would share my experience through my blog posts.

The first thing to know is that I like to use a set of visual design rules when building charts and tables and I like to understand why the rules make sense. In this series of articles I am going to attempt to explain the rules and the reasons behind them. Most of these rules are simple and are based on a solid academic foundation.

In this blog post I would like to introduce the Gestalt Laws, a set of design rules based on research into perception psychology. In the 1930’s the German Gestalt school of psychology investigated how the brain groups and organizes visual shapes. Following this research the so-called “Gestalt” laws were established. These laws form much of the foundation of the techniques I use in table design and I intend to refer to many of them in this series of articles.

Gestalt Law of Proximity: The brain tends to group items together that are close together in space ie. In the same Proximity.

Gestalt Law of Proximity

In the picture above my brain tells me that there are 6 columns of 9 dots in one group.

Gestalt Law of Similarity: We tend to group objects with similar properties (color, shape, texture).

Gestalt Law of Similarity

In the picture above my brain groups the black and gray dots.

Gestalt Law of Continuity: When something is introduced as a series the brain tends to perpetuate the series

Gestalt Law of Continuity

Gestalt Law of Closure: We tend to complete incomplete objects

Gestalt Law of Closure

The table below applies all of the Gestalt laws above:

Table applying Gestalt laws

· The Gestalt Law of Continuity: The right aligned figures and the left aligned text are perceived as columns

· The Gestalt Law of Proximity: The region labels and figures for Scenario W6000 and Scenario W7000 are grouped by having some extra space between the columns.

· Gestalt Law of Closure: Although we have some space between the column quarter column headers and the figures we perceive them as one unit.

· Gestalt Law of Similarity: Formatting the negative numbers red makes them clearly stand out from positive numbers.