Parallel coordinates are a form of information visualisation which allocates each feature a vertical line and then denotes a record or data item as a jagged line between its feature values. This enables the visualisation of multidimensional data with large numbers of features. For the novice they can be initially confusing as one is used to seeing data items as single points, but for the practised user they can reveal interesting patterns in data.
Used in Chap. 18: page 284
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Parallel coordinates
Parallel coordinates visualising data about types of Iris flower. Public Domain from WikiMedia