Click here to see the SAS code.
Click here to see the example.


This is a SAS version (and enhancement) of the following Trellis Plot 
(scroll down to the 'Barley Yield vs. Variety' plot.
Also seen on the graphical excellence page.

Here is some text, quoted from that website, describing the importance of this plot...

"The barley experiment was run in the 1930s. The data first appeared in a 
1934 report published by the experimenters. Since then, the data have been 
analyzed and re-analyzed. R. A. Fisher presented the data for five of the 
sites in his classic book, The Design of Experiments. Publication in the 
book made the data famous, and many others subsequently analyzed them, 
usually to illustrate a new statistical method

Then in the early 1990s, the data were visualized by Trellis Graphics. 
The result was a big surprise. Through 60 years and many analyses, an 
important happening in the data had gone undetected. The above figure 
shows the happening, which occurs at Morris. For all other sites, 1931 
produced a significantly higher overall yield than 1932.  The reverse is 
true at Morris. But most importantly, the amount by which 1932 exceeds 
1931 at Morris is similar to the amounts by which 1931 exceeds 1932 at 
the other sites. Either an extraordinary natural event, such as disease 
or a local weather anomaly, produced a strange coincidence, or the years 
for Morris were inadvertently reversed.  More Trellis displays, a statistical 
modeling of the data, and some background checks on the experiment led to 
the conclusion that the data are in error. But it was Trellis displays such 
as the above figure that provided the ``Aha!'' which led to the conclusion."


For full details of the tricks used to create this plot, see the comments in the code.

But, basically, it's a grouped horizontal bar chart, with most of the bars 
just white (invisible), and markers annotated on the white bars to 
represent the data values.

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