Essential Graphing • Parallel Plots • The Parallel Plot
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The Parallel Plot
To produce the plot shown in The Parallel Plot Report, follow the instructions in Example of a Parallel Plot.
The Parallel Plot Report
A parallel plot is one of the few types of coordinate plots that show any number of variables in one plot. However, the relationships between variables might be evident only in the following circumstances:
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when the variables are side by side
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if you assign a color to a level of a variable to track groups
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if you select lines to track groups
Note: If the columns in a parallel plot use the Spec Limits column property, the specification limits appear as red lines.
Interpreting Parallel Plots
To help you interpret parallel plots, compare the parallel plot with a scatterplot. In each of the following figures, the parallel plot appears on the left, and the scatterplot appears on the right.
Strong Positive Correlation
The following relationship shows a strong positive correlation. Notice the coherence of the lines in the parallel plot.
Strong Positive Correlation
Strong Negative Correlation
A strong negative correlation, by contrast, shows a narrow neck in the parallel plot.
Strong Negative Correlation
Collinear Groups
Now, consider a case that encompasses both situations: two groups, both strongly collinear. One has a positive slope, the other has a negative slope. In Collinear Groups: Parallel Plot and Scatterplot, the positively sloped group is highlighted.
Collinear Groups: Parallel Plot and Scatterplot
Single Outlier
Finally, consider the case of a single outlier. The parallel plot shows a general coherence among the lines, with a noticeable exception.
Single Outlier: Parallel Plot and Scatterplot
Related Information 
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Additional Examples of the Parallel Plot Platform