在 Altair 中更改构面标题位置？

Question

How can I move the facet titles (in this case, year) to be above each plot? The default seems to be on the side of the chart. Can this be easily changed?

import altair as alt
from vega_datasets import data

df = data.seattle_weather()

alt.Chart(df).mark_rect().encode(
    alt.Y('month(date):O', title='day'),
    alt.X('date(date):O', title='month'),
    color='temp_max:Q'
).facet(
    row='year(date):N',
)

Answer 1

One solution is to remove the row specification and set the facet to have a single column

import altair as alt
from vega_datasets import data

df = data.seattle_weather()

alt.Chart(df).mark_rect().encode(
    alt.Y('month(date):O', title='day'),
    alt.X('date(date):O', title='month'),
    color='temp_max:Q'
).facet('year(date):N', columns=1)

Answer 2

A general solution for this is to use the labelOrient option of the header parameter:

df = df[df.date.dt.year < 2014]  # make a smaller chart

alt.Chart(df).mark_rect().encode(
    alt.Y('month(date):O', title='day'),
    alt.X('date(date):O', title='month'),
    color='temp_max:Q'
).facet(
    row=alt.Row('year(date):N', header=alt.Header(labelOrient='top'))
)