Spinning multi-color
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Spinning multi-color 2

Here are two more versions of the greenhouse gas chart.

The first one is a Marimekko which many would consider to be appropriate for this type of data.  It is essentially a stacked bar chart where the width of the bar is scaled to the proportion of the type of gas.  Here's what one would be looking at:

Redo_greenhouse2


Merimekkos (also called Mosaic charts) share many of the problems of pie charts.  Note the need to use multi-color, the difficulty in comparing the areas of the pieces (even worse than looking at sectors), and the difficulty in comparing across categories since the pieces float in irregular space (take for example the three pink pieces).  My rule is: avoid at all costs. (Well, like the pie chart, when the data is sufficiently simple, with very few pieces and with some outliers, these could be acceptable.)


Secondly, here is a recycled junkart chart, with all white space removed from the interior.  (Thanks to Derek for the suggestion.)

Redo_greenhouse3


Depending on what the purpose of the chart is, one can decide what is the base for the proportions.  My version preserves equity between the two dimensions.  Anything else will require the designer to make a choice.  If, for example, the base is 100% for each type of gas emitted, then the reader could not derive from the same chart the proportion of each source of emission (across all types of gases).


Comments

Jon Peltier

I like Derek's suggestion.

Martin

Is the data available? I would like to run it through the different variation of mosaic plots.

(btw. who came up with "Merimekkos"? Mosaic's are just fine; seems to be a good marketing idea to increase attention on an established concept...)

Kaiser

Martin: here is a CSV of the data

Source,CO2,Methane,NO
Industrial processes,20.6%,0.9%,5.9%
Transportation fuels,19.2%,0.0%,1.1%
Agricultural byproducts,0.0%,40.0%,62.0%
"Fossil fuel retrieval, processing and distribution",8.4%,29.6%,0.0%
"Residential, commercial and other sources",12.9%,4.8%,1.5%
Land use and biomass burning,9.1%,6.6%,26.0%
Waste disposal and treatment,0.0%,18.1%,2.3%
Power Stations,29.5%,0.0%,1.1%

Ajay

A bit late to the defence of the Mosaic chart :-) but well if you were to increase the number of categories (from 3 to say 10 (contstrain the chart to the same overall area), the alternate solution would be approaching the "junk" status.

I think mosaics do have value under some circumstances, especially when you don't need to get the exact value but establish a mental map of how each element stands in the grand scheme of things.

Another point taht I think most people miss is that mosaics would seem more 'readable' if they were to be plotted as a square rather than a rectangle. If the chart in the example had been a square, an average reader would have a better chance of being able to 'grasp' (not 'know') the entire picture.

I agree that they share some of the same problems inherent in the pie chart but I would mind if all mosaics should be accorded the junk status.

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