每个邮政编码一个点

此示例展示了一个地理图，其中每个邮政编码有一个点。

方法语法

import altair as alt
from vega_datasets import data

# Since the data is more than 5,000 rows we'll import it from a URL
source = data.zipcodes.url

alt.Chart(source).transform_calculate(
    "leading digit", alt.expr.substring(alt.datum.zip_code, 0, 1)
).mark_circle(size=3).encode(
    longitude='longitude:Q',
    latitude='latitude:Q',
    color='leading digit:N',
    tooltip='zip_code:N'
).project(
    type='albersUsa'
).properties(
    width=650,
    height=400
)

属性语法

import altair as alt
from vega_datasets import data

# Since the data is more than 5,000 rows we'll import it from a URL
source = data.zipcodes.url

alt.Chart(source).transform_calculate(
    "leading digit", alt.expr.substring(alt.datum.zip_code, 0, 1)
).mark_circle(size=3).encode(
    longitude='longitude:Q',
    latitude='latitude:Q',
    color='leading digit:N',
    tooltip='zip_code:N'
).project(
    type='albersUsa'
).properties(
    width=650,
    height=400
)
# No channel encoding options are specified in this chart
# so the code is the same as for the method-based syntax.