20 Toes, 4 Feet, 2 Artists, 1 Passion: Life in numbers

English translation of 20 Zehen, 4 Füße, 2 Künstler, 1 Passion: Life in numbers

Our life can be described with numbers and visualized in diagrams. However, every mean and every chart are simplifications. Useful and fascinating, but also obstructive and restrictive.

Dresden premiere

Yesterday we experienced a wonderful visualization of two “lives in numbers” in the Festspielhaus Hellerau. The two choreographers and dancers Katia Manjate and Anna Till meet in the Dresden premiere of “Life in numbers”. Four years ago, the artists began to compare their lives on the basis of statistics and through these got to know each other. This gave the impulse to “Life in numbers”, and so the piece begins. With a comparison of life in Dresden, where Till lives, and Maputo, where Manjate lives. In the course of the 8 parts, we get to know key data, which are translated into dance on a Cartesian coordinate system, with movements along the invisible x- and y-axes. The dancers themselves form the data points, always in relationship with each other, but changing, converging, and diverging in the course of time.

Differences and similarities

In the middle part of the piece we turn away from the mean values and towards individual data points. No longer: “How long does a woman live in Germany and one in Mozambique” is discussed, but Till and Manjate ask themselves directly: “How old are you?“. The confrontational, curious questions are staged like a duel and bathed in bright light. The shadows of the bodies are projected into rectangles formed by the spotlights, thus visualizing our thinking in boxes. The audience waits with great anticipation for the next answer.

In the third part the tension is released, the light becomes warm and the dance playful. The artists now begin a joyful confrontation with their differences and celebrate their similarities. This is supported by music and rhythms from both countries.

Numbers are beautiful

In the end, Till asks, can we live without numbers? “Life in numbers” answers “no”, but also shows the life within numbers. And it demonstrates that numbers are more than economic values. Numbers may describe how often we laugh per day, how long we see the sun, and what rhythms feet can dance.

As a scientist, I avoid 3D diagrams because they distort data. With “Life in numbers” you can experience how dance, a three- or even four-dimensional visualization, can make numbers directly experienceable and fascinating.

The performance can be seen today and tomorrow in Dresden-Hellerau https://www.hellerau.org/de/event/life-in-numbers/.

19th/20th of October at tanzhausnrd (https://tanzhaus-nrw.de/de/buehne/spielplan) and then in Maputo!

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20 Zehen, 4 Füße, 2 Künstler, 1 Passion: Life in numbers

Tanz als Visualisierung

Unser Leben kann mit Zahlen beschrieben und in Diagrammen visualisiert werden. Jeder Mittelwert und jede Visualisierung sind jedoch immer Vereinfachungen. Nützlich und faszinierend, aber auch behindernd und einengend.

Premiere in Hellerau

Gestern konnten wir im Festspielhaus Hellerau eine wunderbare Visualisierung von zwei „Leben in Zahlen“ erleben. In der Dresden Premiere von „Life in numbers“ treffen sich die beiden Choreografinnen und Tänzerinnen Katia Manjate und Anna Till. Vor 4 Jahren begannen die Künstlerinnen ihre Leben anhand von Zahlen zu vergleichen und sich so kennenzulernen. Dies gab den Impuls zu „Life in numbers“, und so beginnt auch das Stück. Mit einem Vergleich der Leben in Dresden, wo Till lebt, und Maputo, wo Manjate lebt. Im Laufe der 8 Teile lernen wir so zunächst Eckdaten kennen, die tänzerisch auf einem kartesischen Koordinatensystem umgesetzt werden, mit Bewegungen entlang der unsichtbaren x- und y-Achsen. Die Tänzerinnen bilden hier selber die Datenpunkte, immer in einem Verhältnis zueinander, aber im Laufe der Zeit sich verändernd, konvergierend, divergierend.

Unterschiede und Gemeinsamkeiten

Im mittleren Teil des Stücks wenden wir uns von den Mittelwerten ab und den individuellen Datenpunkten zu. Nicht mehr: „Wie lange lebt eine Frau in Deutschland und eine in Mosambik?“ wird erörtert, sondern Till und Manjate fragen sich direkt: „Wie alt bist Du?“. Die konfrontativ-neugierigen Fragen werden wie ein Zweikampf inszeniert und in grelles Licht getaucht. Die Schatten der Körper werden in Rechtecke projiziert, die von den Scheinwerfern gebildet werden und visualisieren damit unser Denken in Kästen. Das Publikum wartet mit der Fragenden höchstgespannt auf die nächste Antwort.

Im dritten Teil löst sich die Spannung, das Licht wird warm und der Tanz spielerisch. Die Künstlerlinnen beginnen nun eine freudige Auseinandersetzung mit ihren Unterschieden und feiern ihre Gemeinsamkeiten. Dies wird von Musik und Rhythmen aus beiden Ländern unterstützt.

Zahlen sind auch schön

Am Ende fragt Till, können wir ohne Zahlen leben? „Life in numbers“ antwortet „nein“, zeigt aber auch das Leben in den Zahlen. Und es zeigt, dass Zahlen mehr sind als ökonomische Werte. Zahlen können auch beschreiben, wie oft lache ich pro Tag, wie lange sehe ich die Sonne, und welche Rhythmen können meine Füße tanzen.

Als Wissenschaftler vermeide ich 3D-Diagramme, weil sie Daten verzerrt zeigen. Bei „Life in numbers“ kann man erleben wie Tanz, eine drei- oder sogar vierdimensionale Visualisierung, Zahlen ganz unmittelbar erlebbar und faszinierend machen kann.

 

Die Vorstellung ist heute und morgen noch in Dresden-Hellerau zu sehen (https://www.hellerau.org/de/event/life-in-numbers/).

Am 19. Und 20. Oktober im tanzhausnrd (https://tanzhaus-nrw.de/de/buehne/spielplan) und danach in Maputo!

Viel Spass!

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Publikumsgespräch mit der Programmleitung und den Künstern

Misleading bar charts #3

We keep discussing axis layouts and the problematic cases of non-zero baselines (in bar charts). Here is another example from the city of Dresden. Dresden is a really pretty place and it is always worth coming for a visit. With the below chart, the city wanted to showcase that each year new record tourist numbers are recorded.

Dresden_tourism.png
Dresden tourist numbers from 2010-2014.

Truthful bar chart

Now, since this isn’t the first time we discuss baselines, you should immediately spot that a rise from around 200,000 to 300,000 isn’t even close to a tripling of number as the bar length visually suggests. And overall, the bar-length does not actually even represent the increase at all. It rather seems that their lengths were chosen to fit an imaginary linear increase. I re-plotted the bar chart with a zero-baseline. Lo-and-behold, the rising number of tourist is still visible, but clearly not nearly as record-worthy.

Dresden_visitors_1
Truthful bar chart reporting Dresden tourist data.

Really truthful bar charts

For each chart, we should not only think about baselines but ask: where do the numbers come from? And, do we see the complete dataset? In this case, the data was collected by the city of Dresden, which should be a reasonably good source for basic statistical data (all data is here: https://www.dresden.de/de/leben/stadtportrait/statistik/wirtschaft-finanzen/tourismus.php).

The image however circulated in 2017 – three years after the last data-point shown! Now, if you know that since the end of 2014 Dresden is plagued by very prominent weekly demonstrations of right-wing activists, having no data after 2014 is alarming. In the local science and business community the problems are very evident: we have a clear drop in international scientists applying and accepting jobs in the city! I therefore went to the Dresden city website to get the data for the subsequent years and this confirmed what I suspected: tourist numbers no longer rose, instead, they even dropped!

Dresden_visitors_2
Dresden tourists 2010-2018. Show all the relevant data – leaving out years might be misleading.

Line or bar chart?

Time trends are usually more  visible in line charts. Indeed, the drop of tourist numbers since 2014 is very apparent in a line chart, and even more so when we leave out the zero-baseline, which somewhat flattens the data (note: in line charts leaving out zero-baseline is ok and sometimes even necessary!).

Fun with Excel

And, did you know you can use a picture as the background for your chart in Excel!?!

 

Dresden_visitors_5

 

 

 

 

 

Misleading bar charts #2

Bar charts encode categorical values by length. By comparing bar lengths, we can visually compare the category sizes.

When a bar is truncated due to a missing zero-baseline or an interrupted y-axis, the relative size difference between the bars changes. Now, the bars no longer visually encodes the actual category value. (Read more from a previous blog)

Misleading bar chart

FOX_news_axislayout.png
A now almost classic example in DataViz for a misleading bar chart

The above is a DataViz classic. FOX NEWS  reported an (to them: alarming) increase in Obamacare enrollments over a few days with a bar chart. They apparently feared imminent bankruptcy of the USA and therfore save the nation by overemphasizing the increase with truncated bar. Instead of the moderate ~20% rise (6 to 7 milllion), their bar showed a 300% increase in length!

Non-misleading representation

I quickly re-designed the chart in Excel. The increase is still clearly visible, even with a zero-baseline.

Excel_modified_zerobaseline
Bar_v2 Same data with zero-baseline. Lower: adjusted axis labeling.

Line or bar chart?

Alternatively, FOX NEWS could have simply used a line chart. Indeed, temporal changes are easier to understand in line charts: our eyes can now follow an upward (increase), or downward (decrease) line. Note: a line chart for 2 time points only is known as a slope chart! 

Even better for FOX NEWS: omitting the zero-baseline is possible in line charts as they only communicate relative changes and focus on the trend and not absolute numbers (more here).

Excel_modified_slopechart
Alternative for temporal data: line chart/slope chart
Obama_realslope
Slopechart focusing on the increase from March 27 to March 31. (H/T Holger Brandl.)

 

Never trust the default!

On a side-note: the default bar chart generated by Excel for this data IS A BAR WITHOUT A ZERO-BASELINE! I am in shock (and obviously don’t use Excel very much)!

So maybe, just maybe FOX NEWS simply used Excel default settings??? Reader, beware: never ever trust a default setting!

Excel_default_nozerobaseline
Excel defaults sometimes are misleading!