我的线条无法在 altair.chart.mark_geoshape 中正确绘制

Question

我需要从this website 绘制爱达荷州的河流

当我将它加载到 geopandas 并尝试通过 altair.Chart().mark_geoshape() 绘制它时，我的图表出现了一堆随机线，它们没有按预期绘制。我不知道发生了什么，因为我是地理空间数据方面的新手。

我遵循此示例中的模式https://altair-viz.github.io/gallery/london_tube.html，但无法绘制线条。

任何想法或我如何做到这一点都会有很大帮助！下面是我正在使用的代码。谢谢！

import altair as alt
import geopandas as gpd
from vega_datasets import data

states = alt.topo_feature(data.us_10m.url,'states')
hydro = gpd.read_file('drive/MyDrive/data_cse350/hyd250/hyd250.shp')

rivers = hydro.loc[hydro.FEAT_NAME.isin(['Snake River','Henrys Fork'])]

rchart = alt.Chart(rivers).mark_geoshape().encode(color = 'FEAT_NAME')

idaho = alt.Chart(states).mark_geoshape(fill = 'white',stroke = 'black').project(
    'albersUsa'
    ).transform_calculate(state_id = "(datum.id)"
    ).transform_filter((alt.datum.state_id)==16)

rchart+idaho```

If you can solve this, that would be great! Thank you for your help! I have already spent waaaayyy too many hours on getting this to work. 

Answer 1

之所以没有画出来，是因为geopandas数据坐标系不同，需要转换成表示经纬度的格式。我对这种事情的经验是有限的，所以我不得不手工弄清楚。我实际上参考了爱达荷州的地图以确保它匹配。

import altair as alt
import geopandas as gpd
from vega_datasets import data

states = alt.topo_feature(data.us_10m.url,'states')
hydro = gpd.read_file('./data/hyd250/hyd250.shp')
hydro_trans = hydro.to_crs(epsg=4612)
rivers = hydro_trans.loc[hydro.FEAT_NAME.isin(['Snake River','Henrys Fork'])]

rchart = alt.Chart(rivers).mark_geoshape(
    filled=False,
    strokeWidth=2
).encode(
    color='FEAT_NAME'
).properties(
    width=600,
    height=300
)

idaho = alt.Chart(states).mark_geoshape(
    fill=None,
    stroke='black'
).project(
    'albersUsa'
    ).transform_calculate(
    state_id = "(datum.id)"
    ).transform_filter(
    (alt.datum.state_id)==16
)

rchart+idaho