Double spam

Thursday, January 15th, 2009

At November 18th I received this email. Unasked. They cannot blame Excel’s diagram wizard for that. It likes to chop axes. But not always. And not with this data.

Good old Times

Thursday, May 15th, 2008

Many cut axes just because of Excel. And go to charting hell. Because when you cut you distort. And when you distort you lie. At least with your graph. The graphical change in your data is no longer proportional to the change in values. He explains it quite well with a demolished graph from the SportAuto magazine. Here is a positive example. From the German newspaper “Die ZEIT”. This newspaper is off the mark sometimes, too.

Strike at the German Post, information on market share and letter volume
Die ZEIT, 2008–04–30, p. 37, market share of Deutsche Post (left) and number of letters in Germany in billions (right)

All my rules are observed. Time runs from left to right. Scale starts at zero. The graph is proportional to its values. No exaggeration. No gadgets. No unnecessary percentage signs. Letters in billions, not in single pieces.

In the same issue another good graph. Structure is shown top-down. Labeling where it belongs: next to the columns. At least for the values. I would have left out the series “andere” (“others”). The dots, too.

The demand for academics rises, data on the automotive sector in Germany
Die ZEIT, 2008–04–30, p. 78, academics in the automotive sector, for automobile manufacturers and suppliers

“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.

Histogram as a mini-graph

Monday, April 30th, 2007

Average and median intend to characterize distributions with a single value. Often, this is not enough. If you want to understand data you have to look at it. Rafe has a nice idea how to do this in an information-dense way.

Mrs. Johnson’s piano class last year had eight students of varying ages pianoclass01, seven of them children and one older gentleman, Mr. Onaip, who provided the other students with an interesting perspective on music and life in general. This year, the age distribution is noticeably different pianoclass01, since Mr. Onaip has brought along two of his like-aged friends and his daughter, Allegro, who has just graduated from medical school.

It works in Excel, too.

How important it is to look at data in detail is demonstrated in the story of Stephen Jay Gould [in German].

Rich tables for high resolution reporting

Thursday, February 15th, 2007

What is better: tables or charts? That was discussed in the past. Some said a chart is worth a thousand words. I think a picture is worth a thousand words. And most charts need a thousand words to be explained. They are so awful, mostly. Because it is so hard to standardize a chart and there are lots of things that can go wrong. Bissantz loves graphic tables. Me too. Charts are tightly integrated into tables. You have the best of both worlds in one concept. Graphic tables are easy to standardize and you can integrate almost every chart type in a table. Sparklines provide time-series. Horizontal bars are good for almost all types of comparisons. Graphic tables maximize data-to-ink ratio. They are fine grained and with high resolution. The graphical elements provide easy orientation for your eyes. The numbers provide all the details. Typical problems of legends and labeling never arise. I provided some examples in the “Radar chart trap” and in “Small things that make a big difference”. Today, I explain how to create waterfall charts in tables.

A waterfall chart is a variant of a bar chart. It shows how an initial value is changed through other values which lead to a final value. In Excel, you can use invisible columns but this is tricky. Rolf has a nice Excel template for free. Data entry is not so easy. Formatting is very nice.

GM scheme Hichert

Jon has programmed an Excel add-in. Formatting is not so easy. Data entry is very nice.

GM scheme Peltier

In both cases a chart is the result. If you turn it around it is still readable, perhaps even better.

GM scheme turned

Turned around it fits perfectly into a graphic table. Subtotals are also easy. This is how Bissantz has done it in DeltaMaster.

GM scheme in Pivot

It is possible in Excel, too. Just use the REPT function and a few tricks. I show you how in an example Excel sheet.

DB-Scheme inExcel

Radar chart trap

Wednesday, December 6th, 2006

In our company, people think a lot about how to present figures well. ‘Well’ means that everybody is able to quickly grasp what they mean. That gives us more time to brood over their impact.

Things become difficult when it comes to radar charts.

Radar chart

The same data is much better off in a graphical table. The most important fact emerges immediately: I am always above average!

Graphical table

Here at the office, they make software that draws these tables automatically. In Excel you would use the Repeat function. That’s quite simple: a vertical bar is repeated as many times as the corresponding data value prescribes. That yields a nice bar inside the cell. You can even label it if you concatenate the value with the “&” character. Here is a sample how that works.