Series 
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A set of data points   Each set of related data points makes up one series. In the
preceding graph, there is a series for Stellar sales, another series
for Cosmic sales, and another series for Galactic sales. Each series
in a graph is distinguished by color, pattern, or symbol. 
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Categories 
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The major divisions of the
data   Series data are divided into categories, which are often non-numeric.
In the preceding graph, the series are divided into four categories:
Q1, Q2, Q3, and Q4. Categories represent values of the independent
variable(s). 
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