Unfortunately, this Sankey diagram has some shortfalls, which qualify it as being a “bad example”. These are:

• Sankey arrow widths are not always to scale (see for example the flow of 7.6 W in the middle labelled “surface”, which is definitely not half the width of the 14.6 W flow marked “Joule loss”)
• Arrows branching out of the main flow are shown as short stubs, just as if the quantity is represented by the length (!) of the arrow, rather than its width. A completely new concept for Sankey diagrams. Have a look at the 0.9 W mini-stub “Surface” in the cone area, and at the 1.2 W stub “Surface” in the linear motor box.
• The diagram uses dotted-dashed frames to mark sections in the diagram, at the same time it uses white arrows with a simple border line for the Sankey arrows. Either colored or grey areas, or colored Sankey arrows would have helped enormously.
• Arrows branch off orthogonally, and to accomadate for the reduced quantity in the remaining flow, the border of the arrow on the opposite side curves in. This is not wrong as such, but rather uncommon, and can best be observed in the linear motor section at the left. Same phenomenon for arrows joining the main arrow. The arrow heads just overlap rather than actually joining the other arrow graphically. The receiveing arrow bulges out on the other side.
• The section between the exhaust heat exchanger and the regenerator is awkward, and probably wrong. How can you branch off 296.6 W and 5.8 from a stream of 320.5 W, and are still able to have a flow of 63.0 W lead away from the remaining flow. I have not yet figured out what the problem is, but possibly the “Carnot minimum” flow was supposed to be drawn the other way round.

When I get to figure out the last issue I might draw this Sankey diagram myself, and post it here.

Daniel used the LLNL 2008 U.S. energy flow charts as model for his Sankey diagrams in Excel. Here is what he came up with (clipped section):

Actually the result is quite close to the original Sankey diagrams, with similar colours, arrow routing, and even the same fonts.

Daniel explains:

“I lightened the colors on the input boxes (had to do it), but otherwise I think my rendition is faithful to the original. I may have stayed too true to flow pipe proportionality. Some of them are so thin they do not print well. This should be addressed. While my pipes are seemingly lined up, they will not survive the chart being resized vertically without some small errors, either gaps in a pipe stack, or overlap.
(…)
An interesting project would be to create an Excel addin that would allow you to specify category box locations and have VBA do all of the grunt work in lining up the flow pipes, automatically creating the chart. (…) In it’s current form no VBA was used. “

So, if you wish to draw a Sankey diagram with the Microsoft Office package installed on your computer, and enjoy using VBA, you might want to give it a shot. Gabor Doka’s Sankey helper (an Excel macro) is another option. Dedicated Sankey diagram software tools are available. It would recommend one of those, if you need to produce more than one Sankey diagram, or wish to make updates to your diagram and layout adaptations more comfortably.

BTW, here is the story on the man behind the Sankey diagrams at LLNL.

At the tip of the joint arrow head you can see the target share price, which is calculated as “the result of mathematically combining all of our forecasts for a company into a single number representing the per share value of the company.” When playing around with the parameters, this value will adapt accordingly.

Here are some examples

Forbes, techCrunch and the New York Times all reported about what the latter calls “America’s Next Top Stock Model”, but none of the mentioned Sankey diagrams though.

Have fun playing around with the models … they have fancy Web2.0-silverlightish animations too. But don’t blame me if the share doesn’t reach the forecasted price

The idea of SankeyTurtle code is to give each Sankey flux – each data cell – an accompagnying instruction how to draw the flux exactly in terms of path and geometry. The SankeyTurtle syntax is based on the vintage Logo TurtleGraphics drawing language, where you tell an imaginary turtle with a pen attached to it’s tail commands like “Move Forward” and “Turn Right 90°” and record the trail of the pen.

This will definitely an exciting improvement for all users of the SankeyHelper freeware … sorry, Sankeyware.

I’ll keep you posted about the progress and any official release.

This is actually quite a nice idea to show the improvements resulting from a technical measure. The diagram on the left represents the original situation, while on the right it is seen in grey. The flow diagram for the new situation overlays the “old” diagram. Both are scaled to 1 kg of varnish applied to a workpiece (the green Sankey arrow), so the reductions in input quantity and emissions show the actual savings achieved.

This is andy’s colorful sample. Quite nice. I especially like the color gradients along the bands, a feature which – to my knowledge – none of the software tools currently supports.

The two arrows branching off to the top in a 90° angle do not maintain their magnitudes, which supposedly represent the quantities, and are drawn at a deliberate width. On top of that, the bases of the arrowheads are about two times as wide as the actual arrow width, thus overemphasizing the flow. Look at the 40% thermal losses which look much larger than the 50% useful work to the right side…

I did play around a little bit with this tiny example, and came up with a number of alternative versions.

Not sure which one is the “best” one, and each has its pros and cons. #1 (hover the mouse pointer over the image to see the number of each alternative version) is very close to the original version. The arrow head size in #3 is more modest. #4 has no explicit spike arrow heads at all. #6 has grey divider lines on most of the horizontal section. I kind of like #7 with color differentiation best, but then again, it is energy that is displayed in all flows.

What do you think? Let me know your favourite or suggestions for improvements in your comment

– translation start –

Volume flow, distribution… flux?

A new chapter in the discussion [polémica] about the ‘scientific’ name of the “little arms” graphics ['gráficos de bracitos'].

Xocas came up with the name ‘volume flow’ diagrams ['gráficos de caudales'] and my vote was for ‘distribution diagram’. Other suggestions were thrown in: Xoán G. made reference to Minard and his ‘capacity diagram’ ['gráfico de aforo']. Herminio J. Fernández voted for cosmography diagrams ['cosmografías'] as refered to by Stovall [Infographics by James Glenn Stovall, Allyn&Bacon, Massachussetts, 1997]. Many others voted for ‘flow diagrams’ ['gráficos de flujo'], although Xocas discarded this suggestion because “the term flow diagram normally refers to a very specific type of visualization of process [flows]. It could be used as a generic term, but has interference with another model”.

Now, there is a new player in our conversation. It is Mario Tascón, who also believes that the correct denomination is ‘flow diagrams’. His justification:
“According to Harris (Information Graphics) and Bruce Robertson (How to make Charts and Diagrams) these graphics are called flow diagrams, and are of the type in the same category which are used as decision diagrams in informatics [computer science]. The latter are more in fashion now [Por motivos de modas], but the former have always [sic!] existed (a historic example is the one of Napoleons troops)”.

Suggestions are welcome in the comments.

– translation end –

I hope I got it more or less correct. It is not easy to find the right translation for the sometimes subtle differences between the terms. For those of you who can read Spanish, please check out the original post and the full discussion thread on Xocas’ blog.

The post is decorated with this beautiful Sankey diagram.

It shows the main earnings and spendings of Spain in 2008 and was produced by Jorge Doneiger and Álvaro Valiño for the daily newspaper Publico in 2007. Values are in million Euros. Flows are to scale, as for as I can see, the ‘impuestos especiales’ in dark black might be en exception.

The top part shows the sources of funding, the bottom part the beneficiary sectors. The fact that the stacked width in the middle is wider than that of the funds distributed suggests that the Spanish state is actually piling up its money, but probably this has to do either with the list of recipients not being complete, or with earnings received in 2008 but not distributed in the same year.

The hand with the coin supports Chiqui Esteban’s vote for naming it a ‘distribution diagram’. Toss a coin in the coffee dispenser and wait for your coffee to be poured… errh, did we have ‘dispenser diagram’ already?

I save the ‘best of comments’ and my reasoning why I still call them Sankey diagrams for another time…

Note (Aug 19): A case of DYRF, do your research first! I just detected that Chiqui himself has an English version of his article here. So, now you got the choice between two versions!

They are absolutely funny, so I am trying to give you a translation of these two blog posts. This is part 1 for a post from March 17 titled “Gráficos de erogación”. I left some words in Spanish and my comments in square brackets.

– translation start –

Distribution Graphics

A couple of months ago, Xocas and I discussed via GTalk what the name, or what should be the name of the diagrams with the little arms ['gráficos de bracitos']. As it turned out, the winner name was volume flow graphics ['gráfico de caudales'].

Today, we decided to withdraw our proposal and we are going to call them ‘distribution graphics’ instead ['gráficos de erogación'].

This is because of the coffee. The coffee machine of my new employer www.lainformacion.com (click the link, we are already up running), shows the message ‘distributing’ ['erogando'] while you wait for your cup to be filled. Looking in the RAE [note: Real Academia Española], the verb ‘erogar’ is defined as:

(Del lat. erogāre).

1. tr. Distribuir, repartir bienes o caudales. [distribute, share the goods or funds]
2. tr. Méx. y Ven. Gastar el dinero. [México and Venezuela: spend money]

This definition is spot on. So we shouldn’t continue to call them ‘little arms’ ['de bracitos'], ‘tubing’ ['de tubería'], ‘squid’ ['de pulpo'], ‘tree-roots’ ['raíces'] or whatever diagrams any more. But don’t say that we didn’t work hard in finding the correct nomenclature. As we have to do. So Tufte will… ['A Tuftear'].

– translation end –

The accompanying Sankey diagram apparently is from the New York Times and shows how 21.4 billion $ in federal aid for NYC after 9/11 were distributed (hey! there you are, a ‘distribution diagram’ ). Funny enough, the caption says: “The figure above is an attempt to bring sources of funds together and show how they add up (sic!) to $ 21.3 billion”.

So what is distribution for one, is “adding up” from another perspective.

Part 2, the translation of “Caudales, erogación… ¿flujo?” and a summary of the comments to follow.

Note (Aug 19): A case of DYRF, do your research first! I just detected that Chiqui himself has an English version of his article here. So, now you got the choice between two versions!

Arup Australasia’s Digital Innovation Team is working on interactive reporting technologies. They say that “… not everyone reads technical reports, so this is the beginning of what’s next – visual reports.”

Check out the video, it is interesting, and watch out for the Sankey diagram seconds 0:15 to 0:21

What we see is a Sankey diagram unfolding in an animated sequence. One step further would be animated Sankey diagrams, like the research project I posted about that came up with a Java/Quicktime animation on energy flows, and this Sankey animatedGIF on CO2 and energy from 1990 to 2015.

Any other animated Sankey diagrams out there…?

This is the ‘Everything Radial’ Circular Sankey Diagram

… and this is the ‘Tangential Fly-off’ Circular Sankey Diagram

One concern seems to be that the proportional arrow magnitude doesn’t work that well, since the human eye perceives the arrow area rather than thickness in such a circular Sankey diagram.

Thanks VisisoGuy for this contribution to the big basket of Sankey diagrams

You can see the oil imports to the United States from January 1973 to August 2008 on a map that depicts the flow quantities as Sankey arrows linking the country of origin and the U.S. If you switch to the unit “Dollar”, you can see the value of the oil imported depicted as Sankey arrows.

One can play the the whole 35-year period as a movie, or use the slider on the time line to see individual months. The data used is from publicy accessible EIA/DOE statistics.

The United States is still 60 % dependent on imported oil. MRI’s MOVE project seeks possibilities to reduce foreign crude oil dependencies. The goal is to “get completely off oil by 2050, led by business for profit.”

Go to the RMI movie page and try it yourself. When I did the Lybia Oil Export map last year I wasn’t aware of this Sankey movie, which is of course much nicer.

The authors consider Sankey diagrams as directed weighted graphs but they “can be difficult, time-consuming, and uninteresting to render by hand”. However, “Sankey diagrams do add an indisputable expressive power to a standard mathematical rendering of a graph…[and] when professionally constructed, Sankey diagrams represent flow in a manner … can be understood by anyone, instantly.”

Three diagrams are presented: a simple directed, weighted graph representing a candy factory, a pen-sketched B/W Sankey diagram, and the corresponding Sankey diagram in SVG format, created using data in XML format and XSLT style sheet transformation.

They also have some interesting details on graphical problems, such as overlay, edge layout, width of Sankey arrows in curves, etc. Basically all that stuff that developers of professional Sankey software tools have to cope with.

This does not fully classify as a Sankey diagram, I think, because the arrows don’t seem to reflect any quantities (number of bugs, time spent on bugs, …). But just like the diagram that showed the number of people having been accused and the turnout of the cases I showed here in June 2007, it visualizes a sequence of breakdowns, leading to decisions that are taken (dashed line arrows).

Now, anybody wants to check their bug tracking tool and show a similar diagram but with real numbers?

One of their Sankey diagrams that dates back to 1999 has an interesting two-part structure. It actually is made up from two Sankey diagrams, which are connected by one flow. Values are in quadrillion BTUs.

The top part of the diagram shows electricity produced from various sources, losses along the production line, and the consumption of the electricity in the “Residential”, “Commercial” and “Industrial” sectors. This is structured very similarly to other Sankey diagrams EIA publishes annually (example).

The bottom part shows another Sankey diagram for electricity produced by ‘Nonutility Power Producers’. So what exactly are these NPPs?

A corporation, person, agency, authority, or other legal entity or instrumentality that owns electric generating capacity and is not an electric utility. Nonutility power producers include qualifying cogenerators, qualifying small power producers, and other nonutility generators (including independent power producers) without a designated franchised service area, and which do not file forms listed in the Code of Federal Regulations, Title 18, Part 141. (Source)

Half of the electricity produced by Nonutility Power Producers in 1999 was fed into the grid, while the other half was consumed on-site. I imagine these are typically larger industrial facilities, that have their own power generation. The fact that nuclear energy appears in this section does irritates me a little bit, but as this page explains, the reason is probably a nuclear reactor in a national research laboratory, that is accounted for here.