基于Bokeh中的x_range自动设置vbar line_width

Question

I have a vbar tied to a ColumnDataSource which gets updated based on some widget selections. If I start with line_width=5 it looks great with my initial data. However, when I update the graph, the x_range gets updated to fit the updated data and causes the relative width of the bars to change.

Ideally, the width should always be proportional to the number of bars displayed. I tried looking at the various properties on the x_range and xaxis to see if I could get the range and try to calculate the width myself but I haven't found anything that helps. Been looking around and the documentation and nothing. Any thoughts?

Answer 1

I finally figured this out with help from @bigreddot. It turns out that I was using the wrong property. Instead of using line_width I needed to use width . Since my x_range is a datetime range, and datetimes are expressed in milliseconds, I needed a large enough width to display correctly. This takes care of setting a proportional width when zooming in, since the width represents a specific period on the x_axis .

Since I have a function to change the freq of how I group my columns and update my ColumnDataSource.data , I just need to re-calculate the width when I update it.

Here's the working code:

def get_data(freq='MS'):
    return pd.DataFrame(srs.groupby(pd.Grouper(freq=freq)).mean())

source = ColumnDataSource(data=ColumnDataSource.from_df(get_data()))

def get_width():
    mindate = min(source.data['date'])
    maxdate = max(source.data['date'])
    return 0.8 * (maxdate-mindate).total_seconds()*1000 / len(source.data['date'])

f = figure(plot_width=550, plot_height=400, x_axis_type="datetime")
f.x_range.set(bounds='auto')
r = f.vbar(source=source, top='volume', x='date', width=get_width())
bar_glyph = f.renderers[-1].glyph

handle = show(f, notebook_handle=True)

and my update function:

def update_data(freq={'Quarter': 'QS', 'Month': 'MS', 'Week': 'W'}):
    source.data = ColumnDataSource.from_df(get_data(freq))
    r.glyph.width = get_width()
    push_notebook()

i = interact(update_data)