Task-based evaluation of multirelational 3D and standard 2D parallel coordinates

Multivariate data sets exist in a wide variety of fields and parallel coordinates visualizations are commonly used for analysing such data. This paper presents a usability evaluation where we compare three types of parallel coordinates visualization for exploratory analysis of multivariate data. We use a standard parallel coordinates display with manual permutation of axes, a standard parallel coordinates display with automatic permutation of axes, and a multi-relational 3D parallel coordinates display with manual permutation of axes. We investigate whether a 3D layout showing more relations simultaneously, but distorted by perspective effects, is advantageous when compared with a standard 2D layout. The evaluation is accomplished by means of an experiment comparing performance differences for a class of task known to be well-supported by parallel coordinates. Two levels of difficulty of the task are used and both require the user to find relationships between variables in a multivariate data set. Our results show that for the manual exploration of a complex interrelated multivariate data set, the user performance with multi-relational 3D parallel coordinates is significantly faster. In simpler tasks, however, the difference is negligible. The study adds to the body of work examining the utility of 3D representations and what properties of structure in 3D space can be successfully used in 3D representations of multivariate data.