1. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 1 Niklas Elmqvist | Purdue University Pierre Dragicevic | INRIA Jean-Daniel Fekete | INRIA “ ” Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation

2. 2 Visualizing Complex Data Complex dataset Complex visualization Many simple visualizations

3. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 3 Motivation  Information visualization is now more than 15 years old  Lots of visual representations  New ones every year at IEEE InfoVis  Varying complexity  Varying purpose  Scatterplots: one of the simplest and most widely used visual representations  Multidimensional data  Examples: SpotFire, ADVIZOR, etc

4. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 4 Scatterplots  Assign dimensions to graphical axes  Two (typical) or three  Data cases as points in the space defined by axes  Additional dimensions  Point color  Point size  Point shape  …  Limited number of displayed dimensions! dimension A dimension B

5. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 5 Problem  Many (most?) interesting real-world datasets have many dimensions  Certainly more than a scatterplot can show!  Two possible solutions: 1.More complex visual representation  Parallel coordinates, DataMeadow, etc…  Lose simplicity of scatterplots 2.Create many scatterplots (one per combination of dimensions)  But how to visualize them?

6. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 6 Scatterplot Matrices  Idea: Create matrix of all data dimensions  Each column/row is a data dimension  Each cell in the matrix is a scatter plot  Reordering of columns/rows (automatic or manual)  Explored by others, but we add a twist:  Use matrix as a space for navigation  Visual exploration becomes a navigation problem  Result: Visualize complex data through sequence of simple visualizations

7. Example: Scatterplot Matrix Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 7

8. 8 Navigating Scatterplots  Idea: Navigating from scatterplot A to scatterplot B using an animated transition  Problem with linear interpolation animation  No semantic meaning to the user  Can be complex to follow  Compounded by large datasets  Can we add meaning to the transition?

9. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 9 Adding Meaning to Transitions  Make the transition between scatterplots in the scatterplot matrix easier to follow:  Restrict to rectilinear movement (no diagonal movement)  Change only one visualized data dimension at a time  Utilize unused third graphical dimension for the new dimension to show during the transition  Metaphor: rotating a 3D scatterplot to show new 2D projection  Like rolling dice to see another side

10. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 10 Using the Third Dimension  Lazy allocation 3rd graphical dimension  Invisible when viewing a 2D scatterplot, so can be assigned any data dimension  Allocation performed only during the transition  Not “true” 3D – we use third dimension as a presentation tool only  Mechanics of performing 3D rotation:  Perspective view: 3-stage animation (extrusion, rotation, projection)  Looks more natural, but requires three steps  Orthographic view: 1-stage animation (rotation)  Only one step, but may look “weird”

11. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 11 Example: 3D Perspective Transition

12. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 12 Putting It Together  ScatterDice application  Built in Java and uses OpenGL through JOGL  Loads multidimensional datasets using the InfoVis Toolkit [Fekete 2004]  Exploration by navigating a scatterplot matrix  3D transitions between adjacent scatter plots  Support reordering of dimensions  Automatic: by correlation between dimensions  Manual: drag and drop of rows columns  Interaction for the navigation is important

13. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 13 Interaction Techniques

14. Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 14 Demonstration

15. Conclusions and Future Work  Idea: Combine multiple simple visualizations using interactive animation  Visualize complex datasets  Provide meaningful transitions  Interaction is a key element  Avoid automated tours  Allow refinement of queries  Future work  Empirical evaluation of this method  Other applications of the same approach? Rolling the Dice: Multidimensional Visual Exploration using Scatterplot Matrix Navigation 15

16. Questions?  Niklas Elmqvist Electrical & Computer Engineering Purdue University West Lafayette, IN 47907-2035 E-mail: elm@purdue.edu Web: http://engineering.purdue.edu/~elm/elm@purdue.eduhttp://engineering.purdue.edu/~elm/