Co-variates and scatter plots
Who works the hardest? I


WsjnpdsmAnother purpose of data graphics is to tell stories, and Wall Street Journal printed one such chart recently.  In this chart (left), the annotations providing a plausible explanation for the ups and downs of NPS' share price are crucial pieces of information.  Together, the words and the line form a strongly suggestive indictment.


The graph has minor problems:

  • Note the use of unequal time intervals: weekends and the Labor Day holiday were omitted because the stock market is closed on those days.  The practice of using unequally sized intervals to represent equal chunks of time is highly distorting and inexcusable, so this special situation should be footnoted.
  • Taking out the axis/grid-line architecture, this graph would look simpler and better if the share price is given after each annotation, and at the start and end of the plotted time period.
  • The title "Research and Development" makes no sense to me.
  • I also wouldn't use "yesterday" which presumes the reader looks at the chart on the day of publication only.

Reference: "Timing of Stock Issue Questioned After Upgrade", Wall Street Journal, Sept 14, 2005.


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