In addition to what texodus has said below, Crossfilter only implements a small subset of what perspective provides. For example, no streaming (although there is a related project from the Heer lab that supports incremental updates - https://github.com/jheer/datavore), only a single level of grouping, only in 1 dimension, and you can only support 16 dimension fields at once (without increasing a constant in the codebase).