Create legend correlating to stacks in a stacked bar chart

Community Support
1

I’m creating a stacked bar plot, where the y axis corresponds to item number and the x axis is quantity shipped. The individual stacks within the plot correlate to the week an item was shipped. I would like a legend that displays the name of the week corresponding to its color.

However, my current legend plots the quantity shipped for each week.

bokehHover
bokehHover841×766 26.3 KB

The DataFrame that I’m using has part numbers as the index, and a date (stored as a string) for the column headers. So to restate: I would like one legend of each color, and that legend corresponds to the column names of my dataframe.

Here’s the code that I’m using to create the graph.

def createGraph(data, drf):
    data.index.name="Item Number"
    weeks = [str(w) for w in data.columns]
    part_nums = sorted(data.index, key=lambda x: int(x), reverse=True)
    
    plt = figure(y_range=part_nums, plot_height=800, plot_width=800, 
                tools=[hover, PanTool(), BoxZoomTool(), BoxSelectTool(), ResetTool(), SaveTool()])
    
    plt.hbar_stack(weeks, y='Item Number', color=Category20[len(weeks)%20], height=.5, source=data, legend=weeks)
    plt.legend.orientation="vertical"
    plt.legend.location="top_right"

    show(plt)

I already access the date through a hover tool - I just can’t get it in the legend how I want it.

Thank you for your time.

2

Sometimes competing desirable outcomes create tension in an API. This is one of those instances. Bokeh has a very nice and handy capability to automatically grouped legends for CDS columns by passing a column name as the legend value. However, if it happens to be the case (as above) that your legend text is the name of the column, but you don’t want grouping, then you see that kind of output in your screenshot.

To fix this, you have to just be explicit, and tell bokeh that the legend value is a value, not a column name:

legend = [value(x) for x in weeks]

using the value function. In this case we need also the list comprehension, since this is for a “stacked” glyph and weeks is a list.

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