---
url: /mosaic/examples/overview-detail.md
---
# Overview + Detail

Select the top "overview" series to zoom the "focus" view below. An `intervalX` interactor updates a selection that filters the focus view. The `line` and `area` marks can apply [M4](https://observablehq.com/@uwdata/m4-scalable-time-series-visualization) optimization to reduce the number of data points returned: rather than draw all points, a dramatically smaller subset can still faithfully represent these area charts.

## Specification

```py \[Python]
import vgplot as vg

walk = vg.parquet("data/random-walk.parquet")

brush = vg.selection.intersect()

view = vg.vconcat(
    vg.plot(
        vg.area_y(walk, x="t", y="v", fill="steelblue"),
        vg.interval_x(bind=brush),
        vg.width(680),
        vg.height(200),
    ),
    vg.plot(
        vg.area_y(data=walk, filter_by=brush, x="t", y="v", fill="steelblue"),
        vg.y_domain("Fixed"),
        vg.width(680),
        vg.height(200),
    ),
)

```