No click event detected for bar charts

Dash Python
1

Hello,

I have a simple bar chart and I try to detect clicks on bars:

app.layout = dhtml.Div([
    dhtml.Div(id='test'),
    dcc.Graph(
        id='graph',
        figure={'data': []}, # Filled in a callback
    ),
])

@app.callback(Output("test", "children"), [Input("graph", "clickData")])
def event_cb(data):
    print(data)
    return ''

Unfortunately, this callback is never called. When I replace “clickData” by “selectedData”, as illustrated in the Uber example, it works.

Thanks.

2

Hi, and thanks for writing in.

This should be working, it’s unclear why the clickData isn’t working. Might be something with the callback feeding graph

Can you try building a version of this with toy data to see if you’re still not registering click events? I would use the app here as a template: https://dash.plot.ly/interactive-graphing

Just replace the graph with a bar chart, and otherwise display the clickData objects. If that’s working, then the issue must be elsewhere in the app.

3

Thanks for the rapid response. It works with a basic example (see below). I will investigate further for my special case.

import json

import dash
import dash_core_components as dcc
import dash_html_components as dhtml
from dash.dependencies import Input, Output

import plotly.graph_objs as go


app = dash.Dash(__name__)

app.layout = dhtml.Div([
    dhtml.Div(id='output'),
    dcc.Slider(
        id='slider',
        min=0,
        max=3,
        value=0,
        marks={i: str(i) for i in range(4)},
    ),
    dcc.Graph(
        id='graph',
        figure={'data': []},
        style={'marginTop': '20px'},
    ),
])

@app.callback(
    Output('graph', 'figure'),
    [Input('slider', 'value')])
def build_graph(v):
    return go.Figure(data=[
        go.Bar(
            x=['x1', 'x2'],
            y=[1, v]
        )
    ])

@app.callback(
    Output('output', 'children'),
    [Input('graph', 'clickData')])
def display_click_data(clickData):
    return json.dumps(clickData, indent=2)


if __name__ == '__main__':
    app.run_server(debug=True)
4

I found the bug. No click signal is sent when hoverinfo='skip':

@app.callback(
    Output('graph', 'figure'),
    [Input('slider', 'value')])
def build_graph(v):
    return go.Figure(data=[
        go.Bar(
            x=['x1', 'x2'],
            y=[1, v],
            hoverinfo='skip',
        )
    ])

Is it expected? If so, it should be mentioned in the docs.

Thanks.

1 Like