[Legend] Size or title padding

đź“Š Plotly Python
1

Hi,
I’m encoutering an issue with a legend: when created using plotly.express, it’s fine
image

When I do it by hand, the first trace overlaps with the legend title
image

Has anyone any idea how to replicate the plotly.express behavior ?

2

Can you provide the code you’re using when you’re not using Plotly Express?

3

Hi @nicolaskruchten,
Thanks for your reply. I’m using:

fig = go.Figure()
for possible_color in dataframe[color].unique():
    tmp_df = dataframe[dataframe[color] == possible_color]
    name = possible_color
    bar_trace = go.Bar(
        x=np.transpose(tmp_df[x].values),
        y=tmp_df[y].values,
        name=name)
    fig.add_trace(bar_trace)

The aim is to create a grouped stacked barchart, unavailable with plotly.express, as far as I known.
Everything works fine, except for the slight legend issue.

4

Interesting. I’m not seeing where you’re setting the legend title here at all?

5

I’m indeed no setting the legend title at all. It’s just there, I don’t really know why…
I do set the figure title, but remove the corresponding code, as it’s unrelevant here.

EDIT: Though it does seem far-fetched to me, maybe the legend title is kept by Dash (the plot is displayed by Dash) when the figure is changed. I feel like this could be an unexpected/unwanted behavior, but I’m going to investigate that.

6

The issue comes indeed from not setting the legend title. When updating a figure in Dash, the previous legend title is kept, but the current legend considers there is not title, thus overlaps it.

7

OK, that seems like it might be a bug then, but can you please share a bit more of your code so we can reproduce it? Is this a Dash app where you first create a figure with px and then update it with a figure created with graph_objects ? There might indeed be some “leftovers” but I’d need more information to confirm and fix it :slight_smile:

8

utils/create_grouped_stacked_barchart.py (fixed version):

import numpy as np
import plotly.graph_objects as go

def create_grouped_stacked_barchart(
        dataframe, x, y, color, customdata=None, hovertemplate=None,
        color_mapping=lambda x: x, fig=None, verbose=False, title=None,
        labels=None):
    """Create grouped stacked bar chart"""
    if fig is None:
        fig = go.Figure()
    if labels is None:
        labels = {}
    for possible_color in dataframe[color].unique():
        if verbose:
            print(possible_color)
        tmp_df = dataframe[dataframe[color] == possible_color]
        name = str(color_mapping(possible_color))
        bar_trace = go.Bar(
            x=np.transpose(tmp_df[x].values),
            y=tmp_df[y].values,
            name=name,
            hovertemplate=hovertemplate,
            customdata=[
                (name, *i)
                for i in tmp_df[customdata].values]
            )
        fig.add_trace(bar_trace)

    layout = {
        'barmode': 'stack', 'height': 600,
        'legend_title': labels.get(color, color),
        'yaxis_title': labels.get(y, y),
        'xaxis_title': (
            f"{labels.get(x[1], x[1])} par {labels.get(x[0], x[0]).lower()}"),
        }
    if title is not None:
        layout['title'] = title
    fig.update_layout(**layout)
    return fig

page.py (relevant parts only):

layout = html.Div([
    dcc.Checklist(id='checkbox'),
    dcc.Graph(id='blah')])

@app.callback(
    Output('blah', 'figure'),
    [Input('checkbox', 'value')])
def create_graph(split_on_handling):
    grouping_columns = ['A']
    if split_on_handling:
        grouping_columns.append('B')
    # data needs as columns: 'A', 'B', 'C', and 'D'
    detailed_df = retrieve_data()
    detailed_df = detailed_df.dropna()

    if split_on_handling:
        fig = create_grouped_stacked_barchart(
            detailed_df, x=grouping_columns, y='D', color='C')
    else:
        fig = px.bar(
            detailed_df, x='A', y='D', color='C')

    fig.update_layout(barmode='relative')
    return fig

The checkbox is unchecked by default. Checking it will change the figure of the graph.