Parallel coordinates are a form of information visualisation which draws gives each feature as a vertical line and then denores a record or data item as a 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 a sone 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 304
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Parallel coordinates
Parallel coordinates visualising data about types of Iris flower. Public Domain from WikiMedia