The reference vectors of the SOM can be visualized using the component plane representation . In this technique the SOM can be thought of as a cake consisting of component layers. Each component plane is a horizontal layer of this cake while each reference vector is a vertical slice. The component planes are visualized by taking from each reference vector the value of the component and depicting this as a colour or as a height on the grid as in figure 2.5. This representation gives information on the distribution of the component values. By viewing several component planes at the same time it is also easy to see simple correlations between components.
Figure 2.5: Component planes representation of a SOM in 2D (a) and 3D (b).