Cutting Stock Problem

Thursday, December 30th, 2010

A value has changed by 2 %. In total. A few effects have improved it. Others have worsened it. The effects and their differences should be visible. And must not be squeezed. Therefore 10 billions are cut off. One ponses.

E.ON Group - Drivers of group Adjusted EBIT 2009 vs. 2008. Source: E.ON AG (ed.), Performance and streamlining, April 2010, page 17.
E.ON Group – Drivers of group Adjusted EBIT 2009 vs. 2008. Source: E.ON AG (ed.), Performance and streamlining, April 2010, page 17; PDF. Dotted lines by me.

Ugh. If anything does not really fit: omit it. Or think twice: why? Perhaps the form does not fit to the data? Or one has only miscalculated. Like here. Everything had fit in neatly.

“You can’t have the pie and eat it, too”

Sunday, March 30th, 2008

Appetite always signals which piece of the pie is biggest. Always? Sort the pieces. How long did it take?

Pie

Sort the bars. How long did it take? Values are the same in both cases.

Bars

Eric has the same example. But while scaling the bars he was tricked by Excel.

Guess what the circular area represents. And?

Circular area as measure

Its even worse in Excel. You can use the diameter to show the value.

Diameter as measure

It’s enough to drive a person mad.

Major German Newspaper loves „Bella Reporting Standards“

Friday, February 29th, 2008

The German Newspaper “Die Süddeutsche” uses graphic tables in its online edition. They show positive and negative deviations. In the same direction. Here, they always quarrel about that. Pro: It’s easy to compare absolute values. It saves space. Contra: You have to learn it first. And you need color.

Stripes are a la mode. No, no, no – forbidden! They emphasize where there is nothing to emphasize. Get rid of them. Lean is beautiful. This goes for bars, too. Just 9 pixels high instead of 14. The idea of graphs in tables is that of wordlike graphics. Graphs as large as a word. Bars don’t need to be larger than the text around them.

Graphic tables in German newspaper DIE SUEDDEUTSCHE

Know what: Sparklines are missing, too. They are the archetype of wordlike graphics. Read their pattern (“SAP came back from a deep fall and now drifts sideways”) or segment by segment (“VW dropped, went sideways, climbed steep, dropped very fast, climbed very steep, dropped again, climbed ever steeper…”). They offer information otherwise unavailable. To be precise: the table had 20 values, now has 440 values. Information density has increased by a factor of 22.

P.S. The sparklines show values from 2007–12–28 to 2008–02–28. You might dispute scaling, e.g. here.

Small things that make a big difference

Wednesday, December 13th, 2006

Edward says: Use sparklines. Sparklines are data words. Or word graphics. A number without a history is boring. And can mislead. Even so, newspapers show lots of individual numbers. Deutsche Telekom’s revenues in the last quarter. The latest unemployment rate. Yesterday’s Dow Jones index. There’s room for a sparkline at the side. The size of a word. It shows nothing but the pattern of the values to date. You immediately understand it though. Whether it was higher some time in the past. Whether it’s been going up or down for a while. Whether it’s currently close to the historical high or low.

Here’s the development of the euro exchange rate compared to the US dollar. Since its introduction as book money on 1 January 1999 until today 1.32. Almost 3,000 values.

1. It’s not a sparkline without a number after it.

A sparkline is not simply a small time series. It needs the number after it. A sparkline doesn’t work without the number. If it’s there, we can see whether the previous numbers were totally different, slightly different, or more or less unchanged. We often don’t need to know things more precisely.

Wrong Right
Germany 37.7
France 130.4
Austria 75.1
Switzerland 56.6
Germany 37.7
France 130.4
Austria 75.1
Switzerland 56.6

You can add minimum or maximum to them if you wish. Or the initial value on the left.
You can’t write anything in the sparkline itself. Otherwise it will become larger than a word again.

2. The number belongs on the right.

The sparkline shows the number’s past. The number is the last point in the time series. That’s why the number belongs there. You should put things next to each other if they belong to each other. If a value’s on the left, you think it’s the first point in the journey through time. That’s why a sparkline’s number always belongs on the right.

The example shows how confusing it is if it’s done wrongly.

Wrong Right

Source: www.businessweek.com, retrieved 2006–12–12. Redesign: Me.

3. Scaling a sparkline impacts its meaning.

Careful! Scaling is important. Sparklines are small. Scaling is therefore very, very important. You often have several sparklines to compare. If you use the same scale for all of them, you are comparing the patterns and magnitudes of the series of values as well. That only works with similar values. If you use individual scales, you are merely comparing the patterns of the series of values. You compare the magnitudes using the numbers.

Scaled identically Scaled individually
South 9,786,026
North 2,812,324
East 743,415
West 140,476
South 9,786,026
North 2,812,324
East 743,415
West 140,476

Bars integrated in the table help you compare.

Scaled individually
South 9,786,026
North 2,812,324
East 743,415
West 140,476

4. Bars or lines?

Bars are easier to read. But they take up more space. I use bars for short time series, and lines for long ones. Mostly.

Short series Long series

5. Sparklines supplement figures, but do not replace them.

Sparklines are extremely nice in tables. Normally, tables show values for a point in time. Then you want to know how it was before then. So add sparklines. Sparklines can be used to incorporate the past of all values in nearly every table. But it’s wrong to omit the values altogether.

League table just with values

Wrong! Sparklines instead of values

Right! Sparklines and values

6. Sparklines like colors, but do not depend on them.

Publishers are still slightly afraid of sparklines. Especially of colored ones. Color printing is so expensive. But they don’t have to be in color. Sparklines work perfectly well without any coloring.

Single-colored

Now Min Max
Unemployment (1991–2009, in millions) 3.4 2.6 4.9

Multi-colored

Now Min Max
Unemployment (1991–2009, in millions) 3.4 2.6 4.9

SparkMaker helps you draw sparklines.