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In Cousin misfit, we looked at a problematic area chart in which the areas on the chart contain no useful information. The lines in a line chart should carry some meaning, and so too should areas in an area chart.

Wsj_samsung

The Wall Street Journal recently printed something that looked like a cross between a column chart, an area chart, and a flow chart.  Whatever it is, the areas of the pieces do not match the data.

The data describes how the TV market is split between the top 5 brands (comprising over 50% of the total unit sales) and all other brands -- basically the six numbers printed on the chart.

The graphical construct can be broken up into three parts: a stacked column (on the left), a stacked column with gaps (on the right), and some connecting areas (which are parallelograms).

The last two parts are unnecessary, and in particular, the parallelograms distort the total areas.

It can be baffling to the reader why the left column is shorter than the right column when both show the identical data.

At first, I thought this is some kind of flow chart illustrating the change in market share over time but that's not the case.

What's wrong with the standard stacked column?


Reference: "Samsung Edges out TV Rivals", Wall Street Journal, Feb 17 2010.


Comments

Bob

I agree, this chart is odd. But, just to be picky, the parallelograms do not change the total area of each segment, as long as the vertical distances are in proportion? Comparing the parallelograms to the rectangular regions that they "replace", each merely adds a triangular area to the top of the rectangle and removes an identical triangular area from the bottom. Or another way of putting it, area = base x perpendicular height.

Jon Peltier

"What's wrong with the standard stacked column?"

Bar charts, column charts, and line charts all suffer from the same issue. Though perfectly utilitarian, they are perceived as boring, and needing of enhancement. Hence 3D effects, shadows, color gradients, overlapping semi-transparent areas, and other funky bells and whistles, like the strange spacing effect in this chart.

William Ockham

It's supposed to look like a TV.

Kaiser

Bob: the areas would not be distorted only if all the parallellograms have parallel sides. But if so, then the designer would have failed to create space between the boxes on the right.

Hermus

Beyond the visual problems you've described, I have a problem with the whole premise of the data. Can you really claim a few giants are ruling when the top 5 brands have barely over half the market?

carlitos

Kaiser: I think Bob is right. The area of the parallelograms doesn't depend on the angle: for each connecting piece it will be the distance between the stacked columns times the market share (assuming the gap width is constant and the heights are the same for each category on both stacked bars, otherwise the connectors are not parallelograms). The area for each category in the composite chart (which I agree is odd) is just the total chart width times the height of each region (constant).

Kaiser

You guys are good! There is no actual distortion in area because the vertical sides are not altered. Thanks for the correction.

Dan

I imagine that perhaps they started off with a standard stacked column chart, but some editor complained that the different shades of pink/peach were two subtle to be differentiated visually, so the chart maker compromised by adding actual spaces between the areas... but only on one side...?

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