Vanishing act

This is a well-executed chart showing the complex dealings between Wall Street firms in the last 40 years.


They found a way to present all the information without criss-crossing lines.  The right column is the clincher.  It listed all the important recent events.

Reference: "Wall Street: RIP", New York Times, Sep 28 2008.

Flows and partitions

Andrew M., a new but loyal reader, didn't like the flow charts used by the EPA to illustrate cleantech.  We had some lively discussion on flow charts before.  The bottom line seems to be that they are difficult beasts to tame, especially when the relationships are complex.  The example shown by Andrew (below) is not particularly horrid in this scheme of things.  It's the abundance of annotations and colors that cause dizziness.


Here's a view of the same data, using a partitioning approach.  The inputs are fixed at 100 units, which I find easier to comprehend, while the original fixed output at 30 units of electricity and 45 units of heat.  And of course, it is a tremendous service to readers not to have to work out the efficiencies.  Tacitness is a vice, not a virtue, in graph-making.


Reference: "Catalog of CHP Technologies", US EPA Combined Heat and Power Partnership.

Embedding logic

Bernard L. (from France) submitted this bubble chart for consideration.  It accompanied an NYT article claiming the absence of evidence of election fraud.  (Of course, as is well-known, absence of evidence is not the same as evidence of absence.  Here, I'm purely interested in data presentation.)

As a seasoned consultant, Bernard asked if a Marimekko chart would be superior.

Nyt_convictions_2 This is one ambitious chart.  Ignoring the bubbles (which are more nuisance than anything), we are asked to interpret data at three different levels of aggregation in one go.

First, there were 95 cases classified into five indictment types.  Second, these cases resulted in either convictions or acquittals/dismissals.  Third, among the cases ending in convictions (the highlighted area), we were shown the occupations of those convicted.

By flattening three levels into one table, some key information is obscured.  For example, how many cases resulted in conviction?  The reader has to compute either 95-25 or 26+31+10+3.  What percent of civil rights violation convictions were committed by party/campaign workers?  It's not 2/3 = 67% (bottom row) but rather 2/2 = 100%.

The following junkart brings out the logic that is embedded in the complicated bubble-table.  While there is a lot on the page, the text labels plus the flow directions allow readers to absorb the data one level at a time.


I have not attempted the Marimekko as I am not a fan of such charts.  You're welcome to try.

Source: "In 5-Year Effort, Scant Evidence of Voter Fraud", New York Times, April 2007.

PS. I will be working through the backlog of reader submissions.  Thanks for your patience.  Keep them coming!


Remark (Apr 25 2007): Thanks to readers for keeping me honest (see comments below).  The conviction rates shown previously were indeed the inverse.  I have now fixed them.

Graphical equity 3

Zuil provides an alternative rendering of the Sankey diagram / flow chart.  This one is surely superior, being easier to understand while capturing more information than the previous example.

Govt_sankey2_1Ultimately, however, this type of chart will please specialists more than the general reader.

It is designed to be purely descriptive, which explains the absolute equality given to each flow, as indicated by the choice of unique colors and/or patterns for each.

As a data graphic, it can be  improved if the designer has a point to make.  In that situation, only the relevant flows can be highlighted while all others stay in the background.

As it stands, this chart murmurs but does not opine.

Reference: "U.S. Energy Flow - 2002", Energy & Environment Directorate, Lawrence Livermore National Laboratory.

Graphical equity 2

Based on my last post, Zuil and Lope engaged in a lively conversation about "flow charts", apparently also called "Sankey charts" in some circles.  Here is an example Zuil found at the EIA site:Govt_sankey

Zuil commented that

Though often difficult to draw, Sankey diagrams are IMHO unbeatable to represent any type of lossless flow (energy, money, fluids, etc).

I mostly agree: flow charts are great at tracing flows, and it's easy to figure out proportional sources and uses from this example.  Moreover, as Lope suggested, it's fun (to read).

But... the data content of this chart is lower than that of the network graph or the Marimekko.  Imagine removing all the lines (arcs) in the network graph: that is what the flow chart includes.  It achieves more readability by simplification.