Univariate Visualization

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Univariate Visualization

• CMSC 120 Visualizing Information
• 2/21/08

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Types of Data

• Qualitative pertaining to fundamental or
  distinctive characteristics
• Nominal unordered (e.g., names, types)
• Ordinal ordered (e.g., cold, warm, hot)
• Quantitative pertaining to an amount of anything
• Discrete isolated intervals
• Continuous unbroken, immediate connection

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Univariate Data

• A single attribute

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Weather Conditions 2/17/08
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Univariate Data

• A single attribute
• Temperature quantitative
• Condition qualitative
• Characterize Observations
• Number
• Type
• Similarity

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The Raw Data A Dot Plot
n 20

• Distance between individual points
• Emphasize clusters, gaps, outliers
• Reveal frequency of each observation

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Frequency Table

• Groups observations by class
• Quantitative an interval or part of the range of
  the sample
• Qualitative a potential value
• Frequency number of observations that fall into
  a class
• Relative Frequency frequency / sample size

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Frequency Table
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Frequency Table
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Stem and Leaf Plots
15 N 150

• Separate each number into a stem (class) and a
  leaf
• Group numbers with the same stems

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Pie Charts

• Useful for qualitative data
• Must sum to 100

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Histograms

• Pictorial representation of a Frequency Table
• Set of boxes whose area represents relative
  frequency of observations per class
• Total Area of all boxes 100
• Shape of histogram determined by box
• Number number of classes
• Width class interval
• Height

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Histogram
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Histogram
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Patterns

• Outliers observations well away from main body
  of data
• Number of peaks (modes) most popular values
• Abrupt Changes

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Shape
Mode
Mean

• Central Values where data appear to be centered
• Spread how spread out the points are
• Symmetry (Skew)

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How to Lie Aggregation

• Process of putting data into groups
• Allows user to compare among groups
• Hides differences between groups
• Too little noise of individual data overwhelms
  overall pattern
• Too much important patterns are hidden within
  groups

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Interval Size 7 Degrees
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Interval Size 14 Degrees
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Shape of Shell Aperture
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Shape of Shell Aperture
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Shape of Shell Aperture
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Shape of Shell Aperture
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Shape of Shell Aperture
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The 5 Number Summary

• Continuous, Quantitative Data
• Order data from lowest value to highest
• Minimum lowest value
• Lower Quartile cuts off ¼ of the data
• Median middle value
• Upper Quartile cuts off ¾ of the data
• Maximum highest value

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25 25 26.1 26.1 27 28 28.9 30.9 35.6 37 39.9 42.1
44.6 44.6 45 45 46 46.4 46.4 46.9 46.9 46.9 48 48.
2 48.9 48.9 48.9 57.9 60.1
Minimum 25
Lower Quartile 30.9
Median 45
Upper Quartile 46.9
Maximum 60.1
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Box and Whisker Plot
Maximum 60.1
Outlier
Largest Non-Outlier
Upper Quartile 46.9
Median 45
50 of Data
Lower Quartile 30.9
Smallest Non-Outlier
Minimum 25
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Shell Shape