Hide the grid in an a specificaltair plot within a set of vstacked plots - altair

Question

I am trying to create a plot composed of 2 charts stacked vertically: a time series chart showing a data and below it a time series chart showing texts representing events on the time axis. I want the data-chart having a grid, but the mark_text chart below not to show an outer line and no grid. I use the chart.configure_axis(grid=False) command to hide the axis but get the following error: Objects with "config" attribute cannot be used within LayerChart. Consider defining the config attribute in the LayerChart object instead.
I can't figure out, where to apply the configure_axis(grid=False) option, so it will only apply to the bottom plot. any help on this would be greatly appreciated. or any suggestion how to implement the label-plot in a different way.
here is my code:
import altair as alt
import pandas as pd
import locale
from altair_saver import save
from datetime import datetime
file = '.\lagebericht.csv'
df = pd.read_csv(file, sep=';')
source = df
locale.setlocale(locale.LC_ALL, "de_CH")
min_date = '2020-02-29'
domain_pd = pd.to_datetime([min_date, '2020-12-1']).astype(int) / 10 ** 6
base = alt.Chart(source, title='Neumeldungen BS').encode(
alt.X('test_datum:T', axis=alt.Axis(title="",format="%b %y"), scale = alt.Scale(domain=list(domain_pd) ))
)
bar = base.mark_bar(width = 1).encode(
alt.Y('faelle_bs:Q', axis=alt.Axis(title="Anzahl Fälle"), scale = alt.Scale(domain=(0, 120)))
)
line = base.mark_line(color='blue').encode(
y='faelle_Total:Q')
chart1 = (bar + line).properties(width=600)
events= pd.DataFrame({
'datum': [datetime(2020,7,1), datetime(2020,5,15)],
'const': [1,1],
'label': ['allgememeiner Lockdown', 'Gruppen > 50 verboten'],
})
base = alt.Chart(events).encode(
alt.X('datum:T', axis=alt.Axis(title="", format="%b %y"), scale = alt.Scale(domain=list(domain_pd) ))
)
points = base.mark_rule(color='blue').encode(
y=alt.Y('const:Q', axis=alt.Axis(title="",ticks=False, domain=False, labels=False), scale = alt.Scale(domain=(0, 10)))
)
text = base.mark_text(
align='right',
baseline='bottom',
angle = 20,
dx=0, # Nudges text to right so it doesn't appear on top of the bar
dy=20,
).encode(text='label:O').configure_axis(grid=False)
chart2 = (points + text).properties(width=600, height = 50)
save(chart1 & chart2, r"images\figs.html")
this is what it looks without the grid=False option:
enter image description here

Answer 1

The configure() method should be thought of as a way to specify a global chart theme; you cannot have different configurations within a single Chart (See https://altair-viz.github.io/user_guide/customization.html#global-config-vs-local-config-vs-encoding for a discussion of this).
The way to do what you want is not via global configuration, but via axis settings. For example, you can pass grid=False to alt.Axis:
points = alt.Chart(events).mark_rule(color='blue').encode(
x=alt.X('datum:T', axis=alt.Axis(title="", format="%b %y"), scale = alt.Scale(domain=list(domain_pd) )),
y=alt.Y('const:Q', axis=alt.Axis(title="",ticks=False, domain=False, labels=False), scale = alt.Scale(domain=(0, 10)))
)
text = alt.Chart(events).mark_text().encode(
x=alt.X('datum:T', axis=alt.Axis(title="", grid=False, format="%b %y"), scale = alt.Scale(domain=list(domain_pd) )),
text='label:O'
)