Six day-by-hour heatmaps under one colour scale and one gradient legend. The commuter double-peak, the campus midday hump and the weekend-shaped park all read at a glance, and so does the plain fact that the park is a fraction of the size of the station.
colorScale.min/max into every
one, so a given count lands on exactly the same fill in every panel. The
grid then draws ONE gradient strip for the whole thing instead of six
identical legends, and hovering a cell traces the same value in every
other panel. Asking for scales.color: 'independent' is
refused with a warning: per-panel shading is the classic way a heatmap
grid misleads. The cell tooltip is one line
(tooltip.compact), because a full card would cover the row it
is captioning. Trellis is a premium feature; without a license it renders
with a trial watermark.