This example demonstrates multidimensional filtering (crossfiltering) on the Iris dataset using four histograms, one per measurement column. Brushing a histogram highlights data points matching the filter in that dimension, with color intensity indicating how many active brushes a data point satisfies—lightest for none, darkest for all. Overlapping brush combinations produce intermediate shades via a cubehelix color interpolator. The visualization uses D3’s `brushX`, `bin`, and `scaleLinear` APIs, plus the d3-rosetta `StateField` and `one` helpers for reactive state and DOM management. Histogram bars animate smoothly via transitions with staggered delays during layer updates.