KNOWLEDGEBASE - ARTICLE #981

Can Prism create SparkLines?

Last modified January 1, 2009

SparkLines is the term coined by Edward Tufte for intense, simple, word-size graphs that convey the essence of a trend without the clutter of axis labels and other details. The idea is that these tiny graphs can be placed alongside text to convey essential trends, without having to divert your attention to more detailed graphs elsewhere on the page. Tufte suggests showing the main trend in gray, and the last point in red for emphasis.

The graph can be shown just as a trend, or also showing normal range values.

 

GraphPad Prism 4 can make a sparkline graph without too much trouble. In the first tab of Format Axes, I chose the option to hide both X and Y axes and turned off the option to show scale bars. The data are shown as point to point line, 1 pt gray, with the last point shown as a red size=1 symbol. I made the graph as 3 inches wide by 1 inch high (Prism won't let you make graphs with either dimension less than one inch). When I exported the graph using File..Export, I chose to shrink it down so the width was 0.75 inch (a choice in the File Export dialog of Prism 4.01). To add the normal range zone, I created two bogus data sets with "data" defining the first and last point of the upper and lower limit. I plotted those data sets with no symbol and no connecting line, but with a gray area fill (for the upper limit) and a white area fill for the lower limit. I used the order tab to plot first the upper limit, then the lower, and then to put the data on top of that.

Scientists usually show complete graphs, with detailed axis labels and legends. Tufte's intriguing idea is that sometimes it is better to just show the trend in a tiny word-size graph. While GraphPad Prism wasn't designed with this in mind, it lets you create SparkLines fairly easily.

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