Facet without column or row

With altair < 3.0, I was able to do this:

[1]
import altair.vegalite.v2 as alt
from vega_datasets import data

source = data.cars()

line = alt.Chart().mark_line().encode(x="Year", y="mean(Miles_per_Gallon)")

line.facet(data=source)

And then, on another jupyter cell, quickly iterate with facet plot with:

[2]
line.facet(data=source, column='Origin')

However, I get Javascript Error: Cannot read property 'length' of undefined when I specify a facet plot without column or row with altair 3.0.

Is there a way to specify a plot and a facet plot from line?

[romainmartinez]

Hi Jake, I can confirm that with the current master branch, both ways of declaring data (with alt.Chart(data) and chart.properties(data=data)) work correctly, even with layered charts. Thank you for the awesome support.

[jakevdp]

Another note, in case it helps your current workflow: in place of the empty facet, you can always do:

line = alt.Chart().mark_line().encode(x="Year", y="mean(Miles_per_Gallon)")
line.properties(data=source)