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Viewing ChangesMonitoring with Treemaps
Steve BettenCatherine Plaisant
Ben Bederson
SmartMoney.com
SmartMoney.com
SmartMoney.com
A different emphasis
SpaceTree
Treemap
180 Pages on a Web Server (1 week)
brightness = number of requests, no size codingi.e. layout stable as long as no page is added/removed
Treemaps for Monitoring
• Selected application: web site monitoring• Monitoring:
– Look for patterns in web page requests over consecutive time periods• Attribute value changes• Simplification: only one attribute (mapped to color)
– Look for web pages that were created or deleted during those weeks• Topology changes
• What are our options?
Choice of attribute
“Value” “Difference of values”
• Change is immediately visible
• OK for 2 periods only• Not clear what happen when users
need to integrate colors changes over several periods.
• Might be more intuitive• but requires to look at
2 values
green = increase; red = decrease(brighter = more change)
brighter = more requests
Time vs. Space Multiplexing
“All-at-once” “Slider”
• More pixels per page• Generalizes to any number
of periods
• Less need to interact • All data available on one
screen• Fewer pixels per webpage
Main ExperimentAll-at-once Slider
Value
Differenceof values
Additional small study looking at Page Creation/Deletion
• “Show only when existing”– Leads to layout shift – Intuitive: does not show
pages that did not exist!
• “Always show”– Always show pages (colored
black when non existing)– Precludes using size coding
• In both cases, small icons can show location of changes
Procedure
• 12 subjects (CS students)– Each subject tested each version
• Training– 10 min Treemap + 10 min each version
• Eight timed tasks• Total duration: about 1 hour 30 minutes• Computer generated datasets
– Most pages have small changes– A small number of pages have significant
changes
Tasks
1. Determine if all the pages in a directory grew in popularity (2 tasks)
2. Find pages with specific patterns of requests e.g. up-down-up (2 tasks)
3. Find deleted pages 4. Find created pages and determine if they
were popular the first time they existed 5. Determine if a specific page grew in
popularity every week (with no pages added i.e. no possible layout shifts)
6. Same as 5 with some pages added ( i.e. possible layout shift)
Results• For many questions, users perform
equally well using any combination
• When searching for patterns (e.g. up-down-up) – “Difference of values” faster than “value”– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted – “Always show” faster than “show only when
existing”– Subjects strongly disliked layout shifts
Results• For many questions, users perform
equally well using any combination
• When searching for patterns (e.g. up-down-up) – “Difference of values” faster than “value”– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted – “Always show” faster than “show only when
existing”– Subjects strongly disliked layout shifts
Main ExperimentAll-at-once Slider
Value
Differenceof values
Value and Slider (Week 4)
Results• For many questions, users perform
equally well using any combination
• When searching for patterns (e.g. up-down-up) – “Difference of values” faster than “value”– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted – “Always show” faster than “show only when
existing”– Subjects strongly disliked layout shifts
Results• For many questions, users perform
equally well using any combination
• When searching for patterns (e.g. up-down-up) – “Difference of values” faster than “value”– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted – “Always show” faster than “show only when
existing”– Subjects strongly disliked layout shifts
Main ExperimentAll-at-once Slider
Value
Differenceof values
Results• For many questions, users perform
equally well using any combination
• When searching for patterns (e.g. up-down-up) – “Difference of values” faster than “value”– “Slider” faster than “all-at-once”
• In tasks where pages were created/deleted – “Always show” faster than “show only when
existing”– Subjects strongly disliked layout shifts
Additional small study looking at Page Creation/Deletion
• Disliked the layout shifts
• In both cases users mostly used the small icons to see location of changes
Subjective Preference• “Difference of values” preferred over “value”
– Saves a step (visually determining the difference)– Easier to see hue shifts than intensity changes
• “All-at-once” v. “slider”– No difference
• Same pattern of preferences for “ease of learning”
• Subjects only used details table to check their guesses based on color alone
• Very few errors• Only half of subjects adjusted the time interval in the “difference in
values and slider” version• User quote: “Different versions are suited to different tasks
Conclusions
• Treemaps can be effective for monitoring• Consider using:
– “difference of values” instead of “value”– “slider” with an option showing “all-at-once”
• Avoid size changes
• To download treemap3.2: www.cs.umd.edu/hcil/treemap3
(future versions will include monitoring capabilities described today)
• Partial support from Chevron-Texaco• Participation of B. Shneiderman and J-D Fekete