App with Interactive buttons and Dropdown menu

Dash Python
1

I am trying to build a Dash app that will support both a drop down menu for each of NY’s 27 districts as well as an interactive bar chart. The dataframe looks like this:

enter image description here

I have written the following code:

import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly.graph_objs as go
import pandas as pd

# Read in the data 
df = districts_change.drop(['TOTAL'], axis=1)

# Get a list of all the districts
districts = districts_change['DISTRICT'].unique()

# Create the app
app = dash.Dash()

# Populate the layout with HTML and graph components
app.layout = html.Div([
    html.H2("New York Congressional Districts"),
    html.Div(
        [
            dcc.Dropdown(
                id="DISTRICT",
                options=[{
                    'label': i,
                    'value': i
                } for i in districts],
                value='All Districts'),
        ],
        style={'width': '25%',
               'display': 'inline-block'}),
    dcc.Graph(id='funnel-graph'),
])


# Add the callbacks to support the interactive componets
@app.callback(
    dash.dependencies.Output('funnel-graph', 'figure'),
    [dash.dependencies.Input('DISTRICT', 'value')])
def update_graph(Districts):
    if Districts == "All Districts":
        df_plot = df.copy()
    else:
        df_plot = df[df['DISTRICT'] == Districts]

    trace1 = go.Bar(x=districts_change['Year'], y=districts_change[('DEM')], name='DEM')
    trace2 = go.Bar(x=districts_change['Year'], y=districts_change[('REP')], name='REP')
    trace3 = go.Bar(x=districts_change['Year'], y=districts_change[('CON')], name='CON')
    trace4 = go.Bar(x=districts_change['Year'], y=districts_change[('WOR')], name='WOR')
    trace5 = go.Bar(x=districts_change['Year'], y=districts_change[('IND')], name='IND')
    trace6 = go.Bar(x=districts_change['Year'], y=districts_change[('GRE')], name='GRE')
    trace7 = go.Bar(x=districts_change['Year'], y=districts_change[('WEP')], name='WEP')
    trace8 = go.Bar(x=districts_change['Year'], y=districts_change[('REF')], name='REF')
    trace9 = go.Bar(x=districts_change['Year'], y=districts_change[('OTH')], name='OTH')
    trace10 = go.Bar(x=districts_change['Year'], y=districts_change[('BLANK')], name='BLANK')


    return {
        'data': [trace1, trace2, trace3, trace4, trace5, 
                     trace6, trace7, trace8, trace9, trace10],
        'layout':
        go.Layout(
            title='District {}'.format(Districts),
            barmode='group')
    }


if __name__ == '__main__':
    app.server.run(port=8000, host='127.0.0.1')

The app runs locally and displays the drop down menu, however, it is broadcasting the same data 27 times instead of the data that is unique to each district.

2

You created the new dataframe df_plot which is/should be unique to each district but you do not use this dataframe when creating the traces. You seem to be using the districts_change dataframe which im guessing contains the data for all districts.

3

Hi Mike - thanks for your reply. I see what you’re saying, do you have a suggestion for how to fix it? I’m a little confused as to how to incorporate all of the elements in concert. This is my first time using Dash.

4

If I understand correctly you just need to use the correct dataframe in the plot:

@app.callback(
    dash.dependencies.Output('funnel-graph', 'figure'),
    [dash.dependencies.Input('DISTRICT', 'value')])
def update_graph(Districts):
    if Districts == "All Districts":
        df_plot = df.copy()
    else:
        df_plot = df[df['DISTRICT'] == Districts]

    trace1 = go.Bar(x=df_plot ['Year'], y=df_plot [('DEM')], name='DEM')
    trace2 = go.Bar(x=df_plot ['Year'], y=df_plot [('REP')], name='REP')
    trace3 = go.Bar(x=df_plot ['Year'], y=df_plot [('CON')], name='CON')
    trace4 = go.Bar(x=df_plot ['Year'], y=df_plot [('WOR')], name='WOR')
    trace5 = go.Bar(x=df_plot ['Year'], y=df_plot [('IND')], name='IND')
    trace6 = go.Bar(x=df_plot ['Year'], y=df_plot [('GRE')], name='GRE')
    trace7 = go.Bar(x=df_plot ['Year'], y=df_plot [('WEP')], name='WEP')
    trace8 = go.Bar(x=df_plot ['Year'], y=df_plot [('REF')], name='REF')
    trace9 = go.Bar(x=df_plot ['Year'], y=df_plot [('OTH')], name='OTH')
    trace10 = go.Bar(x=df_plot ['Year'], y=df_plot [('BLANK')], name='BLANK')


    return {
        'data': [trace1, trace2, trace3, trace4, trace5, 
                     trace6, trace7, trace8, trace9, trace10],
        'layout':
        go.Layout(
            title='District {}'.format(Districts),
            barmode='group')
    }


if __name__ == '__main__':
    app.server.run(port=8000, host='127.0.0.1')
5

Yes, that did it! Thank you!

1 Like