Visual Variables: Difference between revisions

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Marks can be
Marks can be
* Points
* '''Points''' are dimensionless locations on the plane, represented by signs that obviously need to have some size, shape or color for visualisation.  
Points are dimensionless locations on the plane, represented by signs that obviously need to have some size, shape or color.  
* '''Lines''' represent information with a certain length, but no area and therefore no width. Again lines are visualised by signs of some thickness.
* Lines
* '''Areas''' hava a length and a width and therfore a two-dimensional size.  
Lines represent information with a certain length, but no area and therefore no width. Again lines are visualised by signs of some thickness.
* '''Surfaces''' are areas in a three-dimensional space, but with no thickness.
* Areas
* '''Volumes''' have a length, a width and a depth. They are thus truly three-dimensional.
An area has a length and a width and therfore a two-dimensional size.  
* Surfaces
Surfaces are areas in a three-dimensional space, but with no thickness.
* Volumes
A volume has a length, a width and a depth. It is thus truly three-dimensional.




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=== Characteristics ===
=== Characteristics ===
The choice of the variable, which would be most appropriate to present each aspect of information depends on the caracteristics.
The choice of the variable, which would be most appropriate to present each aspect of information depends on the characteristics.


* Selective
* '''Selective:''' If a mark changes in this variable and it can be selected by the other marks easily the visual variable is said to be selective.
If a mark changes in this variable and it can be selected by the other marks easily the visual variable is said to be selective.
* '''Associative:''' Several marks can be grouped across changes in other visual variables.
* Associative
* '''Quantitative:''' If the difference between two marks in this variable can be interpreted numerically, the visual variable is quantitative.
Several marks can be grouped accross changes in other visual variables.
* '''Order:''' If the variable supports ordered reading it is an ordered visual variable. This means that a change could be read as more or less. e.g. in size you can order according to the area of the marks.
* Quantitative
* '''Length:''' The length defines how many values the variable features. For example how many shades of grey can be recognised.
If the differnce between two marks in this variable can be interpreted numerical, the visual variable is quantitative.
* Order
If the variable supports ordered reading it is an ordered visual variable. This means that a change could be read as more or less. e.g. in size you can order according to the area of the marks.
* Length
The length defines how many values the variable features. For example how many shades of grey can be recognised.


== References ==
== References ==

Revision as of 17:47, 30 October 2006

Information may not have a direct visual manifestation. Therefore one needs to map this information to a visual representation. This is done by visual varibles.

Definition

Marks

A mark is made to represent some information other than itself. It is also referred to as a sign.

Marks can be

  • Points are dimensionless locations on the plane, represented by signs that obviously need to have some size, shape or color for visualisation.
  • Lines represent information with a certain length, but no area and therefore no width. Again lines are visualised by signs of some thickness.
  • Areas hava a length and a width and therfore a two-dimensional size.
  • Surfaces are areas in a three-dimensional space, but with no thickness.
  • Volumes have a length, a width and a depth. They are thus truly three-dimensional.


Visual Variables

Jaques Bertin defined seven Visual Variables [Bertin, 1967] consisting of:

Since nowadays information is presented by computers, the addition of motion as a new visual variable becomes important.

Characteristics

The choice of the variable, which would be most appropriate to present each aspect of information depends on the characteristics.

  • Selective: If a mark changes in this variable and it can be selected by the other marks easily the visual variable is said to be selective.
  • Associative: Several marks can be grouped across changes in other visual variables.
  • Quantitative: If the difference between two marks in this variable can be interpreted numerically, the visual variable is quantitative.
  • Order: If the variable supports ordered reading it is an ordered visual variable. This means that a change could be read as more or less. e.g. in size you can order according to the area of the marks.
  • Length: The length defines how many values the variable features. For example how many shades of grey can be recognised.

References

  • Proceedings
[Bertin, 1967] Bertin, Jaques: "Sémiologie Graphique". Paris: Editions Gauthier-Villars. Deutsche Übersetzung von Jensch, G.; Schade, D.; Scharfe, W.: Graphische Semiologie.Diagramme – Netze - Karten. Berlin: Walter de Gruyter, 1974.
[Skupin, 2000] Skupin, A: "From Metaphor to Method: Cartographic Perspectives on Information Visualization" IEEE Symposium on Information Visualization. October 9-10, 2000, Salt Lake City, Utah.
[Carpendale, 2003] M. S. T. Carpendale: "Considering Visual Variables as a Basis for Information Visualisation", University of Calgary, Department of Computer Science, 2001-693-16, 2003