Search code examples
pythonplotdata-sciencebokeh

Create Legend Label for Quad glyph - Bokeh

I have a Quad plot displaying 2 data-sets. I would like to add a legend to the plot, however I am not sure how to do this with the Quad glyph.

Previous examples have used 'legend' however this is now deprecated, and I've tried using 'legend_label' however this is does not work. My ultimate goal is to use the legend to interactively display both datasets

    # Convert dataframe to column data source
    src1 = ColumnDataSource(Merged_Bins)
    src2 = ColumnDataSource(Merged_Bins)

    #------------------------------------------------------------------------------------------------
    # Plot Histogram using Bokeh plotting library
    #------------------------------------------------------------------------------------------------

    plot = figure(y_range=Range1d(start=0, end=Max_Histogram_Value),sizing_mode="scale_width",width=3000,height= 600,
                  title= "Histogram Plot",
                  x_axis_label="Time (ms)",
                  y_axis_label="Count",toolbar_location = "below")
    plot.yaxis.ticker = FixedTicker(ticks=list(tick_vals))


    glyph1=Quad(bottom=0, top='Delay1', left='left1',
              right='right1', fill_color='#FF7F00',
              line_color='black', fill_alpha=0.7,line_alpha=0.5,name="Option 2")
              
    glyph1_plot=plot.add_glyph(src1, glyph1)
    glyph2=Quad(bottom=0, top='Delay2', left='left2',
              right='right2', fill_color='#616261',
              line_color='#616261',line_alpha=0.1, fill_alpha=0.1,name="Original Design")
              
    plot.add_glyph(src2, glyph2)

    # Add hover tool for when mouse is over data
    hover1 = HoverTool(tooltips=[('Delay Envelope', '@Bin_interval'),('Count', '@Delay1'),('Count Original', '@Delay2')],mode='vline',renderers=[glyph1_plot])
    plot.add_tools(hover1)
    plot.legend.location = "top_left"
    plot.legend.click_policy="hide"
    # Set autohide to true to only show the toolbar when mouse is over plot
    plot.toolbar.autohide = True
    script, div = components(plot)
    show(plot)

enter image description here

Solution

  • It works just fine if you use the Figure.quad method instead of manually calling Figure.add_glyph with an explicitly created instance of Quad. All legen_* arguments are parsed by glyph methods of the Figure class - the glyph classes themselves do not use them at all.

    from bokeh.io import show
from bokeh.plotting import figure

p = figure()
p.quad(-1, 1, 1, -1, legend_label='Hello')
p.quad(1, 3, 3, 1, color='green', legend_label='there')

show(p)

    Alternatively, if you really need the manual approach for some reason, you can also create a legend manually by creating an instance of the Legend class and by adding it to the figure with Figure.add_layout.

    Also, on an unrelated note - your plot looks like it was created with vbar instead of quad because all bars seem to have the same width. If so, perhaps using vbar would be simpler in your case.