Working with lines

Here's how a great idea can be made better.

The unifying axis on the right hand side, described as "comparable percentage-change scales", is a great concept.  The data being plotted are the cumulative percent return for each stock from the start of 2006 to the day of publication.

If the three lines are superimposed, we can see the relative performance throughout the year.  Within these three stocks, Walgreens has clearly underperformed until recently.  Also, plotting weekly rather than daily returns reduces clutter.  The only grid-line of importance is the 0% line, which is what is left.

In addition, the three other axes, depicting actual prices, are redundant; removing them significantly enhances readability. 

Some will insist that actual prices must be shown; the following includes key bits of data in a subtle way.

Reference: "Drugstores are Looking More Like a Growth Story", New York Times, Sept 10 2006.

Comments

[derek]

Also, getting rid of those stupid and distracting pictures. It would not have been so bad if they all occupied rectangles of equal size, but one is a rectangle, the next is a quadrangle that leads the eye upwards from the first, and the third is some sort of weird house shape. The whole collection makes it impossible to compare the lines because of the optical illusions caused by the strong picture envelopes.

Even if they had all been rectangles of equal size, there would have been a danger of optical dragging that can be caused by one picture being stronger than another.

[Sérgio N]

Great blog! One of my recent findings. Thanks!

Btw, what software do you use to plot your graphics?

[Jon Peltier]

The bottom chart, split into thirds to allow for selective price labels, loses more information in terms of vertical resolution. Too great a price to pay for hardly relevant price information. If you can so easily follow the trends, as in the first reworking of the data, then the closing price built into a series data label is the only price that's really necessary.

[Jens Meiert]

Quite a good chart junk example. Though, you could of course improve the combined chart (#2) by slightly different lines in case they're viewed/printed without color.

[merle]

Minor point, but isn't the middle chart mislabeled? It appears that Walgreens and Rite-Aid got switched.

[Kaiser]

Thanks Merle. It's great to know that some of you are reading the details. I fixed the chart titles.

[fatbear]

Hate to say it, but there seems to be some basic problem with your charts - i.e., Walgreen's is at 49.64 as I write this, but your chart says it closed recently at 4.51; Rite-Aid is now at 4.72, but the chart has a recent 51.48. Did you by any chance fix the info around the wrong way?

[Kaiser]

Fixed the wrong chart! This set should be right.