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pythongeopandasfolium

Folium choropleth map not colouring from geopandas

I have a geopandas dataframe (dfg) with the following structure

lsoa11cd           object
A8                float64
OBJECTID            int64
LSOA11CD           object
LSOA11NM           object
LSOA11NMW          object
Shape__Area       float64
Shape__Length     float64
geometry        geometry

I have tried to generate a choropleth via folium, but all the regions are showing as a flat grey.

    m = folium.Map(
    location=[52.2405, -0.9027],
    
    zoom_start=13  
)
folium.Choropleth(
    geo_data=dfg,
    name ='choropleth',
    data=dfg,
    columns=['LSOA11CD', 'A8'],
    
    Fill_colour='RdPu',
 
    fill_opacity=0.5,
    line_opacity=0.2


).add_to(m)



folium.LayerControl().add_to(m)
m

All the regions draw correctly, but all the same colour.

It works nicely using the plot function

dfg.plot(column='A8')

I feel like I am missing something obvious

Solution

  • I think you are missing the key_on parameter in the folium.Choropleth, which is basically the link between your GeoJson and your pandas DataFrame.

    It uses your GeoJson keys to know where to do the join. It can be something like 'feature.id', but you will have to provide an example of your GeoJson so that I can tell you the exact key.