Seeking Help with Implementing a Clickable Radius Feature in Dash for a USDA Data Choropleth Map

Dash Python
1

I’m new to Dash and currently working on a project involving a large dataset from USDA. I’ve successfully created a choropleth map at the county level, but I’m facing challenges with a specific feature. I need to implement functionality where clicking on a county triggers a radius (user-defined) that highlights all counties within that radius. The aim is to either display the values of these counties directly on the map or present them in a table format. I’m unsure about how to approach the radius feature and would appreciate any guidance or suggestions.

like I said new here but eager to learn and hope I can get some clarity.

Thanks!

2

Hello @Conorl86,

Welcome to the community!

It might be helpful if you create an example of the code to get started with finding some help.

3

I’d suggest looking into using dl.Map(dl.FeatureGroup([dl.LocateControl(locateOptions={‘enableHighAccuracy’: True, ‘drawMarker’:True, ‘flyTo’:True, ‘showCompass’:True}),dl.EditControl(id=“edit_control”) ])) then just return the results of the section drawn on map into a callback-based off the “edit_control” Input and using it to run the functions for filtering sites before returning a table or counter component.

4

Also check out this video, you might find it helpful for some aspect of your project: https://www.youtube.com/watch?v=OVggxyO81CQ&t=1132s

5 
        fig = px.choropleth(filtered_data, geojson=counties, locations='fips', color='Value',
                            color_continuous_scale="Viridis",
                            scope="usa",
                            labels={'Value':'productiontest'})
        fig.update_layout(margin={"r":0,"t":0,"l":0,"b":0}, clickmode='event+select')

    elif trigger_id == 'choropleth-map':
        fig = go.Figure(current_figure)

        if clickData:
            clicked_fips = clickData['points'][0]['location']
            centroid = centroids.get(clicked_fips)
            if centroid:
                lat, lon = centroid.y, centroid.x
                circle_radius_degree = 50 / 69  

                fig.add_shape(
                    type='circle',
                    xref='x',
                    yref='y',
                    fillcolor='blue',
                    opacity=0.3,
                    x0=lon - circle_radius_degree,
                    y0=lat - circle_radius_degree,
                    x1=lon + circle_radius_degree,
                    y1=lat + circle_radius_degree,
                    line_color='blue',
                )

    return fig

return fig

this is how I was trying to do it

6

Ok I’ll check this out yeah I was thinking I might have to change the library I use for the map