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InfographicscoursebookVersion1.2 (8February2014)FreeUniversityofBolzanoBozen–PaoloColetti
IntroductionThis book contains the infographics course’s lessons held at the Free University of Bolzano Bozen.
This book is in continuous development, please take a look at its version number, which marks important changes.
Disclaimers
This book is designed for novice data analyzers. It contains oversimplifications of reality and many technical details are purposely omitted.
TableofContentsINTRODUCTION ....................................................... 1
TABLE OF CONTENTS ................................................ 1
1. BASIC NOTIONS ............................................... 1
1.1. FUNDAMENTAL SCOPES .................................... 1 1.2. VARIABLES ..................................................... 2 1.3. SCALES .......................................................... 3
2. TRADITIONAL GRAPHS ..................................... 4
2.1. ONE NOMINAL VARIABLE .................................. 4 2.2. ONE SCALE VARIABLE ....................................... 5 2.3. NOMINAL VERSUS NOMINAL VARIABLES ............... 7 2.4. NOMINAL VERSUS SCALE VARIABLES .................... 8
2.5. SCALE VERSUS SCALE VARIABLES .......................... 8 3. SPECIFIC CHARTS ........................................... 13
3.1. DATA MAP ................................................... 13 3.2. TIME SERIES .................................................. 15
4. MISLEADING FACTORS ................................... 19
4.1. DISTRACTIBLE ELEMENTS ................................. 19 4.2. ELEMENTS IN THE WRONG PLACE ...................... 19 4.3. WRONG PROPORTIONS BETWEEN DATA AND SIZES 20 4.4. DIFFERENT UNITS OF MEASURE ......................... 21 4.5. NOT STARTING FROM ZERO .............................. 22 4.6. TWO AND THREE DIMENSIONAL GROWTH ........... 22
1. Basicnotions
1.1. Fundamentalscopes
Every time we need to represent anything, being a picturesque view through a painting, numbers through a table or, as it will be the case in this book, numbers through a picture, we must never forget what is the scope of our work. To help us in this task, the following questions can give good hints. They can be used every time we are faced with a representation to point out the bad aspects and to find out possible corrections and improvements.
Whatisrepresented?
Representing something without having a prior knowledge of what is going to be represented is clearly pointless, but there are numerous examples of representations built up only to impress the viewer, without any intention of really display something.
Paolo Coletti Infographics course book
Page 2 of 23 Version 1.2 (08/02/2014)
The topic which is displayed must be clear in the designer’s mind and also the point which wants to be underlined must be clear. All the image must be dedicated to these two tasks without adding worthless extras and without depriving these two points of any of their aspects for other secondary scopes.
Issomethingmisleading?
The most widespread problem in data visualization are misleading graphs, which deliberately or by ignorance display information in a wrong way to attract the viewer’s attention to the scope of the representation in an unfair way. The typical example of error are wrong proportions, displaying elements of the picture not in relative scale to each other. This may seems a childish trick, easy to discover; however, when it is done using multidimensional pictures it needs a careful eye to be spotted, a can be seen in section 0.
Issomethinguseless?
Too many graphical representations incorporate elements which do not have anything to do with the main scope, with the only task to embellish the graphics. Very often these elements distract the attention, when not moving the viewer’s focus completely away. In some cases they make parts of the representation incomprehensible, as can be the case when fancy fonts are used to write labels and numbers.
Issomethingmissing?
Very often a graphical representation needs also text and numbers. Even though most of it can be stored in the caption, it is necessary that axes contain the units of measure and their scale, that colors contain a proper legend and that, in case useful information is omitted, it be explicitly cited and explained.
A scaleless or unitless graph is useless even when all elements to compare are in scale, any difference which seems huge can instead be irrelevant. A representation with missing relevant details leads immediately the suspect that the designer wanted to hide something.
Last but not least a time indication is fundamental. Data will change in time while the representation stays the same (unless it is fully interactive) and can be looked at even many years after. With a missing time indication the representation is worthless, it can be referred to right now as well as to 3 millennia ago.
Canotherinformationbeadded?
This question has two aspects. The positive one is checking whether the graph can support other useful details to be stored inside without driving attention away from the main points and without decreasing its comprehensibility. The negative one is making sure that no other useless information is stored inside the graph, better keeping it simple than overloading it with useless elements.
1.2. Variables
We follow Stevens theory1 and we distinguish the data that we have in three big categories, which are treated in different ways both by statistics as well by graphical representations.
Scale variables, also called numeric variables, are data expressed in a numerical format, be it continuous or discrete, on which mathematical operations make sense. They are usually physical measures, such as time, age, weight, distance in Kilometers, length, number of children, GDP.
Nominal variables, also called categorical variables, are data which represent categories. No mathematical operation makes sense on them, even though sometimes numbers are used to identify the categories. Their only scope is dividing the population into categories. For example, country of residence, sex, degree course. Even though scale variable could divide the population into categories, the fact that they have many possible values, even infinite values when the variable is continuous, using them to divide the
1 Stevens, S. S. (1946); On the Theory of Scales of Measurement; Science, vol. 103, n. 2684, pages 677–680.
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• the area plot, which is identical to the line plot but has the area below the line colored. This is many times a misleading element, as it gives the impression that values between two categories really exist (they do not, on the horizontal axis we have only categories not a continuous variable);
• all the three dimensional versions of these graphs are also commonly used. However, unless there is a strong necessity for an extra dimension, this is only extra graphics which moves the focus away from the main point and confuses the viewer.
2.2. Onescalevariable
Two graphs are used to represent the distribution of one scale variable, both requiring grouping procedures.
The most famous is the histogram. It is built deciding a priori a subdivision into intervals of the possible variable’s values and then counting how many cases falls into each interval. The result obviously depends on the choice of intervals, which should be chosen wisely, as too few intervals would result in a useless histogram, while too many intervals would produce an up and down histogram with many 0 cases or 1 case intervals.
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2.5.1. Bubblecharts
When the two variables on the horizontal axes do not share the same unit of measure, as for example population and GDP, it is more effective to use another representation, known as bubble chart. In this representation one of the scale variables is displayed increasing the size of bubbles, either the diameter or the area (even though a two dimensional distortion comes into play, see section 4.6). Moreover, colors can be used to represent a fourth nominal or scale variable.
Website www.gapminder.org has a tool to display several bubble charts which move with time, thus introducing also another dimension. However, it works only on their data.
In order to produce bubble charts on personal data Google Developers’ bubble chart can be used. It does not have an easy to use time feature, but its charts can even be inserted on websites. All its specifications are on https://developers.google.com/chart/interactive/docs/gallery/bubblechart (September 2013) and are summarized here below.
ProducingbubblechartswithGoogleDevelopers
First of all, in order to produce a bubble chart and being able to test, an appropriate HTML file should be created following these steps:
1. create a plain text file, open it with Notepad and copy inside it this code; <html> <head> <script type="text/javascript" src="https://www.google.com/jsapi"></script> <script type="text/javascript"> google.load("visualization", "1", {packages:["corechart"]}); google.setOnLoadCallback(drawChart); function drawChart() { var data = google.visualization.arrayToDataTable([ ['ID', 'Life Expectancy', 'Fertility Rate', 'Region', 'Population'], ['CAN', 80.66, 1.67, 'North America', 33739900], ['DEU', 79.84, 1.36, 'Europe', 81902307], ['DNK', 78.6, 1.84, 'Europe', 5523095], ['EGY', 72.73, 2.78, 'Middle East', 79716203], ['GBR', 80.05, 2, 'Europe', 61801570], ['IRN', 72.49, 1.7, 'Middle East', 73137148], ['IRQ', 68.09, 4.77, 'Middle East', 31090763], ['ISR', 81.55, 2.96, 'Middle East', 7485600], ['RUS', 68.6, 1.54, 'Europe', 141850000], ['USA', 78.09, 2.05, 'North America', 307007000] ]); var options = { }; var chart = new google.visualization.BubbleChart(document.getElementById('chart_div')); chart.draw(data, options); } </script> </head> <body> <div id="chart_div" style="width: 900px; height: 500px;"></div> </body> </html>
2. close Notepad and change the extension of the text file from .txt to .html; 3. double click on the file and open it in your browser, pressing “Allow blocked content”; 4. go back to the file’s directory, right click the mouse on the file and choose “Open with”, then
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Paolo Coletti Infographics course book
Page 12 of 23 Version 1.2 (08/02/2014)
colors will be used. If fourth variable is nominal, a list of colors for all categories is needed. For example colors: ['red','#004411','black','orange']
hAxis: specifies the horizontal axis parameters, is followed by curled brackets and the following sub parameters - direction: 1 or ‐1 for reverse direction - format: a format string for numeric axis labels. For example format:'#,###%' to display
percentages and 3 decimal digits - gridlines: to specify color and count of the gridlines (use same color as background to have no
gridlines), enclosed by curled brackets. For example gridlines: {color: 'white', count: 4} - logScale: true or false - textPosition: 'out', 'in' or 'none' - textStyle: text style for axis’ font. See bubble.textStyle on page 11 for example. - ticks: a vector of numbers indicating where ticks should go. For example ticks: [5,10,15,20] - title: string with the axis’ title - titleTextStyle: style of the title, for example titletextStyle: { fontSize: 9, color: ‘red’} - maxValue and minValue: maximum and minimum value for the axis For example hAxis: {title: 'Life', titleTextStyle: {color: 'black', bold: true}, textStyle: {fontName: ‘Arial’}, minValue: 55, maxValue: 90, ticks: [60, 65, 70, 85], maxValue: 90}
vAxis: specifies the vertical axis parameters, same as hAxis
legend: specifies the legend parameters, is followed by curled brackets and the following sub parameters - position: 'right', 'top', 'bottom', 'in' or 'none' - alignment: 'start', 'center' or 'end' - textStyle: legend’s text style. See bubble.textStyle on page 11 for example. For example legend: {position: 'top', textStyle: {color: 'blue', fontSize: 16}}
sortBubblesBySize: if true it sorts the bubbles by size so that the smaller bubbles appear above the larger bubbles. If false, bubbles are sorted according to their order in the data
title: text to display above the chart. For example title: 'Chart of revenues by cost'
titlePosition: 'in', 'out' or 'none'
titleTextStyle: title text style. See bubble.textStyle on page 11 for example.
tooltip: specifies the tooltip parameters, is followed by curled brackets and the following sub parameters - textStyle: tooltip’s text style. See bubble.textStyle on page 11 for example. - trigger: 'focus' to display the tooltip when the user hovers over an element, 'none' to avoid
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For example, some parameters can be var options = { axisTitlesPosition: 'out', backgroundColor: 'white', bubble: {opacity: 0.4, stroke: 'blue', textStyle: {fontSize: 11, color: 'brown'} }, chartArea:{left:100,top:50,width:"70%",height:"60%"}, colors:['red','#004411','orange'], hAxis: {title: 'Life', titleTextStyle: {color: 'black'}, minValue: 55, maxValue: 90, ticks: [60, 65, 70, 75, 80, 85]}, vAxis: {title: 'Fertility', logScale: true, maxValue: 6, ticks: [1,2,3,4,5], gridlines: {color: 'white'} }, height: 800, width: 1200, legend: {position: 'bottom', textStyle: {color: 'blue', fontSize: 16} }, title: 'Correlation between life expectancy, fertility rate and population of some world countries (2010)', tooltip: {trigger: 'focus'} };
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Page 14 of 23 Version 1.2 (08/02/2014)
Exports by sea of French wines in 1864, source C.J. Minard 1865. 1999 volume of minutes of voice telecommunication. Only the principal route pairs are shown to avoid
cluttering the map. Circular symbols on capital cities represent the country's total annual outgoing traffic,
source http://mappa.mundi.net and www.telegeography.com
3.1.1. Statsilksoftware
A very efficient free software which gives the opportunity to load a map below and data from a spreadsheet, displaying them over the map in a variety of ways including side graphs is developed by Statsilk www.statsilk.com and comes in three packages:
StatPlanet, a web‐based and desktop software for visualizing spatial data through interactive maps, graphs and charts
StatTrends, a web‐based and desktop software for visualizing any kind of data through interactive graphs and charts
StatWorld/StatPlanet, a web‐based and desktop software for exploring world statistics from various international organizations through interactive visualizations.
These programs are interactive, meaning that graphs’ proprieties can be changed with a simple click and web‐based, meaning that they can work through a browser connected to Statsilk’s website.
Infographics course book Paolo Coletti
Version 1.2 (08/02/2014) Page 15 of 23
3.2. Timeseries
3.2.1. Financialchart
Financial data use scale variables time, low price, high price, open price and close price and the main interest is usually depicting prices as a function of time. They have the property that low is always smaller than all the others and high is always larger than all the others. Therefore they can be represented using a candlesticks chart, where time is on the horizontal axis, the central rectangle has values open and close as extremes (and is white or green when open is the base, black or red then close is the base) and the vertical line goes from low to high. In this way five different scale variables can be efficiently represented together. Sometimes traded volume or other indicators is depicted as a daily column plot below the chart, using the same horizontal time line.
Special care must be taken when producing or observing a financial graph for missing values, either because the security is not traded (market closed or security suspended) or because of data errors; in cases like this it is preferable to leave a blank space if just one of the four prices is missing.
Paolo Colet
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Page 18 of 23 Version 1.2 (08/02/2014)
Figurative map of the men losses of the French army in the Russian campaign 1812‐1813, source C.J. Minard 1869.
A new chart of history, source Lectures on History and General Policy by J. Priestley 1788.
Infographics course book Paolo Coletti
Version 1.2 (08/02/2014) Page 19 of 23
4. Misleadingfactors
4.1. Distractibleelements
Any element which is not directly related to the focus of the representation should be avoided, especially when it is only an embellishment of the chart. The typical example is inserting pictures which do not help comprehensibility inside bar plots.
As can be seen in these two pictures, the elements added in the column bars do not help the comprehensibility at all. They do not represent, as they could be, neither the years nor the three analyzed variables in the second graph, where it could be much better displaying a picture related to the variable itself. Their only task is to distract the viewer in the first one with the help of a three‐dimensional object (see section 4.6) and in the second one from the non‐zero start of vertical axis (see section 4.5).
Source Beautiful Evidence by E. Tufte. Source Day Mines 1974 Annual Report.
In this picture instead a fancy left to right perspective effect has been introduced. Its effect on a better comprehensibility of the data is none, while it makes comparing the bars a very difficult task and gives the impression of a much larger increase.
Black columns represent New York State aid to localities in billions of USD, total column represent total budget, source New York Times 1 Feb 1976.
4.2. Elementsinthewrongplace
The position of elements must be planned with special care, as the viewer can induce that it contains a special meaning. In case it does not, this must be evident. For example, in one of the versions of the worldwide famous billion dollar gram, which depicts some of the world’s expenditures on a two dimensional scale. The graph is without any doubt very impressive and efficient in comparing some
Paolo Coletti Infographics course book
Page 20 of 23 Version 1.2 (08/02/2014)
expenses to others. However, apart from the impact on the viewer, there is no need to use two dimensions, one dimension is enough as the variable to be displayed is only one. The only advantage in using two dimensions is the possibility to easily slip insert some rectangles inside other ones. However, this automatically induce into the viewer the idea that a rectangle is part of the outside one, as it is correctly depicted for Online Advertising as part of Worldwide Advertising Spend. However, the viewer is expected to see the same for Iraq War, but the three rectangles are not in the total one, giving the impression of a larger expense.
Upper part of billion dollar gram by D. McCandless, source www.informationisbeautiful.net
4.3. Wrongproportionsbetweendataandsizes
Respecting proportions between numerical data and graphical elements’ sizes is one of the basic principles of any visual representation. In the billion dollar gram the proportion to be respected is between numerical data and areas, but the Facebook area, which correspond to 15 billion USD, should be less than one third of Bill Gates area, which evidentially is not as can be estimated with a simple ruler. The picture below shows instead a billion dollar gram where no evidently wrong proportion or no wrongly placed element seem to appear.
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