quality {SOMbrero} | R Documentation |
Compute SOM algorithm quality criteria
Description
The quality
function computes several quality criteria
for the result of a SOM algorithm.
Usage
quality(sommap, quality.type, ...)
Arguments
sommap |
A |
quality.type |
The quality type to compute. Two types are implemented:
|
... |
Not used. |
Value
The quality
function returns either a numeric value (if only
one type is computed) or a list a numeric values (if all types are computed).
The quantization error calculates the mean squared euclidean distance between the sample vectors and their respective cluster prototypes. It is a decreasing function of the size of the map.
The topographic error is the simplest of the topology preservation measure: it calculates the ratio of sample vectors for which the second best matching unit is not in the direct neighborhood of the best matching unit.
Author(s)
Madalina Olteanu olteanu@ceremade.dauphine.fr
Nathalie Vialaneix nathalie.vialaneix@inrae.fr
References
Polzlbauer G. (2004) Survey and comparison of quality measures for self-organizing maps. In: Proceedings of the Fifth Workshop on Data Analysis (WDA'04), Paralic, J., Polzlbauer, G., Rauber, A. (eds) Sliezsky dom, Vysoke Tatry, Slovakia: Elfa Academic Press, 67-82.
See Also
Examples
my.som <- trainSOM(x.data = iris[,1:4])
quality(my.som, quality.type = "all")
quality(my.som, quality.type = "topographic")