Adding labels to bokeh pie chart wedge

Question

I am new to bokeh, and want to render a pie chart using bokeh figure.

I used the reference from https://docs.bokeh.org/en/latest/docs/gallery/pie_chart.html in order to create my pie chart figure.

Now, I need to add on each part of the pie chart a label which represent the percentage of this part, and the label position should be align to the center.

I could not find a simple way to do it via the documentation, and try to find ways to do it manually, like this example: Adding labels in pie chart wedge in bokeh

I tried to create a label set and add the layout to the plot but i could not figure out if there is a way to control the label position, size, and font. text_align (right, left, center) does not do the job for me.

Here is my code - this function create and return an html of the pie chart The chart argument contains the relevant data for the chart. in this case its a tuple (size 1), and series[0] contains the name of the series (series.title), list of x values (series.x), and list of y values (series.y)

def render_piechart(self, chart):
    """
    Renders PieChart object using Bokeh
    :param chart: Pie chart
    :return:
    """
    series = chart.series[0]
    data_dict = dict(zip(series.x, series.y))
    data = pd.Series(data_dict).reset_index(name='value').rename(columns={'index': 'Category'})
    data['angle'] = data['value'] / data['value'].sum() * 2 * pi
    data['color'] = palette[:len(series.x)]
    data['percentage'] = data['value'] / data['value'].sum() * 100
    data['percentage'] = data['percentage'].apply(lambda x: str(round(x, 2)) + '%')

    TOOLTIPS = [('Category', '@Category'), ('Value', '@value'), ('Percentage', '@percentage')]

    fig = figure(title=series.title,
                 plot_width=400 if chart.sizehint == 'medium' else 600,
                 plot_height=350 if chart.sizehint == 'medium' else 450,
                 tools='hover', tooltips=TOOLTIPS, x_range=(-0.5, 1.0))

    fig.wedge(x=0, y=1, radius=0.45, start_angle=cumsum('angle', include_zero=True),
              end_angle=cumsum('angle'), line_color='white', fill_color='color',
              legend='Category', source=data)

    fig.title.text_font_size = '20pt'

    source = ColumnDataSource(data)

    labels = LabelSet(x=0, y=1, text='percentage', level='glyph', angle=cumsum('angle', include_zero=True),
                      source=source, render_mode='canvas')

    fig.add_layout(labels)

    fig.axis.axis_label = None
    fig.axis.visible = False
    fig.grid.grid_line_color = None

    return bokeh.embed.file_html(fig, bokeh.resources.CDN)

And this is the results: pie chart consist of 3 parts

pie chart consist of 10 parts

in the 2 examples - the series title is 'kuku' x and y values for the first example: x=["A", "B", "C"] y=[10, 20, 30]

and for the second example: x=["A", "B", "C", "D", "E", "F", "G", "H", "I"] y=[10, 20, 30, 100, 90, 80, 70, 60, 30 , 40 ,50]

I know that in the past i could do it easily with Donut but it is deprecated. I want to be able to get something like this one: example1 or this: example2

Higem Higem · Accepted Answer · 2020-01-04T08:42:29

The problem, as you understand, is here:

labels = LabelSet(x=0, y=1, text='percentage', level='glyph', angle=cumsum('angle', include_zero=True), source=source, render_mode='canvas')

It's a bit confusing to create labels in Bokeh, but still: you should add columns like 'text_pos_x' and 'text_pos_y' for every row you draw and fill it in with coordinates where you would like to place the text. And then apply it in LabelSet function, giving x='text_pos_x' and y='text_pos_y' so that every single part of plot have its own coordinates where to place a label:

labels = LabelSet(x='text_pos_x', y='text_pos_y', text='percentage', level='glyph', angle=0, source=source, render_mode='canvas')

and yes, it's necessary to set angle = 0 to avoid text being rotated.

Adding labels to bokeh pie chart wedge

1 Answers