For discussion of what Data Point should be considered as an Outlier, please read What is an Outlier?
Below you can find two charts, demonstrating Visualization of outliers, top chart is Radar Chart and lower Chart is the Box-and-Whiskers Diagram.
The first chart below shows the number of visitors to website, by time of the day; those quantities averaged over time, grouped by the Day of the Week and stacked on top of each other starting from beginning of the week (Monday) up to the end of the Week (Sunday in this case) so daily trends are visualized as well as average weekly picture! It is easy to see that around 11pm and 4am of the each day number of visits far exceeded any other time of the day and either require more attention from sales person(s) who are trying to convert visitors to customers or analyze those visits more details.
Such analysis giving a simple answer: those two spikes in web visits are created by so called Web crawlers and spiders, who are schedules to visit this particular website at this time and therefore those visits should be completely ignored!
The next Chart below is a sample of how the Box-and-Whisker Diagram can be used to Visualize a Snowfall (shown is data points for Monthly Snowfall in Newport, VT during 1977-2007).
Learn more about Box-n-Whisker Plots on the lower part of this page What is an Outlier?
PCA can help you determine the best back end and front end tools for your data and applications to create data visualization with maximum value for your users. Contact us directly at 617-527-4722 or visit the contact us page.