Color parameter in Plotly express doesn't adjust with dynamic selection.

[RammySekham]

I have dynamic dropdown list, which sets the color of labels for the graph.But when selection has one element in it throws an error, otherwise it works fine.

app_graph2`=px.scatter(df, x="MAX_TEMP", y="DEMAND", color="STATE", title='Scatter Plot Demand Vs Maximum Temperature')

I have dcc.dropdown for STATE with multi=True, it throws error, when user selects one state.

      plotly\express\_chart_types.py", line 252, in line
      return make_figure(args=locals(), constructor=g
      o.Scatter)

      plotly\express\_core.py", line 1852, in make_figure
      for val in sorted_group_values[m.grouper]:

Is there any alternative to resolve it ?

Thanks!

[nicolaskruchten]

That sounds like a bug, but I'd need a fully-runnable example to debug it, can you provide one?

For example, this works just fine with a single value for b...

import pandas as pd
import plotly.express as px

df = pd.DataFrame(dict(a=[1,2,3], b=["c", "c", "c"]))

px.scatter(df, x="a", y="a", color="b")

[RammySekham]

Thanks. I think problem is with callback, I am not able to figure it out. But when dashboard screen uploads, there is no data in the graphs. Even I refresh the dashboard it still doesn't update graph. But, when I change dcc components and refresh , it updates. Link

My code :

from dash import dash
import dash_html_components as html
import plotly.express as px
import sqlalchemy as db
from textwrap import dedent
from dash.dependencies import Input, Output, State
from FlaskApp.dashapp.sqlqueries import *

from FlaskApp.dashapp.dashcontrols import *


def init_dashboard(server):
    """Create a Plotly Dash dashboard."""
    dash_app = dash.Dash(
        server=server,
        routes_pathname_prefix='/dashapp/',
        external_stylesheets=[dbc.themes.SUPERHERO]
    )

# Data Connection
engine = db.create_engine('sqlite:///.//data//master.db')
connection = engine.connect()

# Get values for controls
state = get_unique(connection, "data", "STATE")
year = get_unique(connection, "data", "YEAR")
week_flag = get_unique(connection, "data", "Weekened_Flag")
holiday_flag = get_unique(connection, "data", "Holiday_Flag")
connection.close()

# Build Components
controls = [
    dcc_multiselect(id="states", label="State", values=state),
    dcc_multiselect(id="years", label="Year", values=year),
    option_menu(id="week_flag", label="Weekend_Flag", values=week_flag),
    option_menu(id="holiday_flag", label="Holiday_Flag", values=holiday_flag),
    dbc.Button("Refresh", color="primary", id="button_refresh"),
]
app_graph1 = dcc.Graph(id="app_graph1", style={"width": "800px", "height": "400px"})
app_graph2 = dcc.Graph(id="app_graph2", style={"width": "800px", "height": "400px"})
card1 = dbc.Card(controls, body=True)
card2 = dbc.Card([dcc.Markdown(id="sql-query")], body=True)

# Create Layout
dash_app.layout = dbc.Container(
    fluid=True,
    children=[
        html.H1("A dash embedded application for electricity forecast in FLASK",
                style={'color': '#ff6600',
                       'fontSize': 20, 'textAlign': 'center'}),
        html.Hr(),
        dbc.Row(
            [
             dbc.Col([card1, card2], md=3),
             dbc.Col([app_graph1, app_graph2], md=4),
            ]
         ),
        ],
    style={"margin": "auto"},
)

@dash_app.callback(
    [
        Output("app_graph1", "figure"),
        Output("app_graph2", "figure"),
        Output("sql-query", "children"),
    ],
    [Input("button_refresh", "n_clicks")],
    [
        State("states", "value"),
        State("years", "value"),
        State("week_flag", "value"),
        State("holiday_flag", "value"),
    ],
)
def update(n_clicks, states, years, week_flag, holiday_flag):
    if len(states) == 1:
        states = "('" + states[0] + "')"
    else:
        states = tuple(states)

    if len(years) == 1:
        years = "('" + str(years[0]) + "')"
    else:
        years = tuple(years)
    query = dedent(
        f"""
        SELECT CAST(DEMAND AS DECIMAL(10,2)) AS DEMAND, MAX_TEMP, MIN_TEMP, STATE, YEAR, Holiday_Flag, Weekened_Flag 
        FROM data 
        WHERE
        STATE IN {states} AND
        YEAR IN {years} AND
        Weekened_Flag = '{week_flag}' AND
        Holiday_Flag = '{holiday_flag}';
        """
    )
    df = connect_read_sql(query=query, engine=engine)
    connection.close()

    #data manipulation

    df1 = pd.DataFrame({'DEMAND': df.groupby(['STATE', 'YEAR'])['DEMAND'].sum()}).reset_index()

    #figures
    app_graph1 = px.line(df1, x="YEAR", y="DEMAND", color="STATE", title='Electricity Consumption in Australia')
    app_graph1.update_xaxes(type='category')
    app_graph2 = px.scatter(df, x="MAX_TEMP", y="DEMAND", color="STATE",
                            title='Scatter Plot Demand Vs Maxmimum Temperature')

    return app_graph1, app_graph2, f"```\n{query}\n```"

return dash_app.server

`

[gvwilson]

Hi - we are trying to tidy up the stale issues and PRs in Plotly's public repositories so that we can focus on things that are still important to our community. Since this one has been sitting for several years, I'm going to close it; if it is still a concern, please add a comment letting us know what recent version of our software you've checked it with so that I can reopen it and add it to our backlog. Thanks for your help - @gvwilson