GenomeSpy loads ten measurements and computes the count and mean for each group using an aggregate transformation. Each point is a group summary. Zoom or Shift-drag a brush, then read the summaries inside that region into the app.
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Input records contain group and value. The
app receives group, count, and
mean through
view.data.read({scope, limit}); it never loads the
input or repeats the aggregation. Page code sends the returned group
keys to selection.setValue(keys) to highlight the
results using conditional opacity.
Zooming and brushing choose which summaries to read; they do not recompute the groups. “All loaded records” also reads summaries outside the viewport or brush. A cleared brush returns no summaries. Synthetic generic data.