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