Stack visualization

[axelboc]

Creating an epic for now, as this is quite complex.

• Create a stack visualization to allow visualizing for nD datasets where n is in the interval [2, 3] (at least initially).
• Users navigate on one of the dimensions with a slider (typically the first dimension).
• The (n-1)D dataset can then be visualized with the appropriate visualization (scalar, matrix, line chart, heatmap, etc.)

The definition above is quite generic but the two main use cases are visualizing a 2D dataset as a stack of line charts, and a 3D dataset as a stack of heatmaps.

[axelboc]

This is done as well - the Matrix, Line and Heatmap visualizations support nD datasets.