Python trying to overlay points on a chloropleth map with plotly

user_17630036 0
Viewed 42

I'm trying to create a map of the US with states filled in using Chloropleth depending on a value and specific location points overlaying the map.Assume the data is something like this:

data = {'state_code': ['AZ', 'NY', 'IL', 'CA'],
    'lat': [33.44838, 40.7648, 41.8842, 34.052235],
    'lon': [-112.07404, -73.935242, -87.6324, -118.243398],
    'count': [2,7,5,5 ]
    }
df = pd.DataFrame(data)

Count is the variable I want to use to fill in the states and I want to map the longitude and latitude of the cities as points.

This is what I have tried:

fig = go.Figure()

fig.add_trace(
px.choropleth(df,
                locations='state_code', 
                locationmode="USA-states", 
                scope="usa",
                color='count',
                color_continuous_scale="viridis",                 
                ))
fig.add_trace(
px.scatter_geo(df, 
           lon = df['lon'],
           lat = df['lat'],
           mode = 'markers',
           marker_color = "Red",
           ))
fig.update_layout(
    title = 'Title'
)

fig.show()

I get the following error:

ValueError: 
Invalid element(s) received for the 'data' property of 
    Invalid elements include: [Figure({
'data': [{'coloraxis': 'coloraxis',
          'geo': 'geo',
          'hovertemplate': 'state_code=%{location}<br>count=%{z}<extra></extra>',
          'locationmode': 'USA-states',
          'locations': array(['AZ', 'NY', 'IL', 'CA'], dtype=object),
          'name': '',
          'type': 'choropleth',
          'z': array([2, 7, 5, 5], dtype=int64)}],
'layout': {'coloraxis': {'colorbar': {'title': {'text': 'count'}},
                         'colorscale': [[0.0, '#440154'], [0.1111111111111111,
                                        '#482878'], [0.2222222222222222,
                                        '#3e4989'], [0.3333333333333333,
                                        '#31688e'], [0.4444444444444444,
                                        '#26828e'], [0.5555555555555556,
                                        '#1f9e89'], [0.6666666666666666,
                                        '#35b779'], [0.7777777777777778,
                                        '#6ece58'], [0.8888888888888888,
                                        '#b5de2b'], [1.0, '#fde725']]},
           'geo': {'center': {}, 'domain': {'x': [0.0, 1.0], 'y': [0.0, 1.0]}, 'scope': 'usa'},
           'legend': {'tracegroupgap': 0},
           'margin': {'t': 60},
           'template': '...'}})]

The 'data' property is a tuple of trace instances
that may be specified as:
  - A list or tuple of trace instances
    (e.g. [Scatter(...), Bar(...)])
  - A single trace instance
    (e.g. Scatter(...), Bar(...), etc.)
  - A list or tuple of dicts of string/value properties where:
    - The 'type' property specifies the trace type
        One of: ['bar', 'barpolar', 'box', 'candlestick',
                 'carpet', 'choropleth', 'choroplethmapbox',
                 'cone', 'contour', 'contourcarpet',
                 'densitymapbox', 'funnel', 'funnelarea',
                 'heatmap', 'heatmapgl', 'histogram',
                 'histogram2d', 'histogram2dcontour', 'icicle',
                 'image', 'indicator', 'isosurface', 'mesh3d',
                 'ohlc', 'parcats', 'parcoords', 'pie',
                 'pointcloud', 'sankey', 'scatter',
                 'scatter3d', 'scattercarpet', 'scattergeo',
                 'scattergl', 'scattermapbox', 'scatterpolar',
                 'scatterpolargl', 'scattersmith',
                 'scatterternary', 'splom', 'streamtube',
                 'sunburst', 'surface', 'table', 'treemap',
                 'violin', 'volume', 'waterfall']

    - All remaining properties are passed to the constructor of
      the specified trace type

    (e.g. [{'type': 'scatter', ...}, {'type': 'bar, ...}])
choropleth plotly geo python
2 Answers

The plotly express methods chloropleth() and scatter_geo() return Figures, not data traces as your code expects.

Plotly Express is good for quick, simple charts, but less appropriate for complex layered charts with mixed data like what you have here. For those, you should probably use plotly.graph_objects Instead of plotly.express. See examples of graph_objects.Cloroplethmapbox() and graph_objects.Scattermapbox().

Other than the examples, I also find the full graph_objects documentation to be helpful when trying to customize plots.

user_21127220

As @Sarah Messer answered, it is not possible to overlay an express map on a graph object, so the map comes in an additional format in the graph object. Specifically, the following code will achieve this.

fig = go.Figure()
fig.add_trace(go.Choropleth(
                locations=df['state_code'], 
                locationmode="USA-states", 
                z=df['count'],
                colorscale="viridis",                 
                ))

fig.add_trace(go.Scattergeo(
    lon = df['lon'],
    lat = df['lat'],
    mode = 'markers',
    marker_color = "red",
    hovertemplate='%{lon},%{lat}<extra></extra>',
))

fig.update_layout(
    autosize=True,
    height=450,
    title = 'Title',
    geo=dict(
        scope='usa'
    )
)

fig.show()

enter image description here

user_131078040
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