Vega Altair visualization notes

Mon, 21 Sep 2026 00:00:00 +0200

Top-Level Chart Configuration — Vega-Altair 6.3.0.post4+gb2ca919d documentation All together with .properties on the Chart object itsel: alt.Chart().encode().properties().top_level_configuration_item()

Encodings — Vega-Altair
- Channels (x,y etc.): Channels — Vega-Altair
- Encoding data types:
  - Shorthand syntax¹
    - Q: quantitative: ‘a continuous real-valued quantity’
    - Discrete/categorical:
      - O: ordinal (=sortable)
      - N: nominal (=not sortable)
    - T: temporal, G: geojson
Faceted charts (=multiple side-by-side):
- Layered & Multi-View Charts — Vega-Altair 6.3.0.post4+gb2ca919d documentation
- Simple:
  - .encode(x=..,y=..,column=xxx,row=yyy
Sorting
- Sorting | Vega-Lite

Rendering multiple altair charts in a single cell of a jupyter notebook
```
graph[0].display()
graph[1].display()
```
Legends
- Disable: alt.Color().legend(None) (! not inside Color()!)
- Multiple legends
  - Displaying Two Different Legends in hconcat Chart Using Altair - GeeksforGeeks
  - Scale & Guide Resolution — Vega-Altair 6.3.0.post4+gb2ca919d documentation
```
.encode(
	alt.X("variable"),
	alt.Y("count()"),
	alt.Color("value:N", legend=alt.Legend(title="x")),
	# TIL 
	alt.Scale(scheme='blues') # make colors different too
)
#...
alt.vconcat(*charts).resolve_scale(color="independent")
```
- API: altair.Legend
New lines to labels
- passing a list of strings instead of string makes them newlines[^²]
- labelExpr="replace(datum.label,'_','\\n')" doesn’t seem to work for newlines
  - Customizing Visualizations — Vega-Altair 6.3.0.post4+gb2ca919d documentation
    - takes us to d3-format | D3 by Observable for formatting a la python, :.2f only for numbers
  - more on this: Dynamic Behaviors with Parameters | Vega-Lite

Py/Altair on serhii.net