I love how easy it is to set up basic hover feedback with HoverTool, but I’m wrestling with a couple aspects of the display. I have time-series data, with measurements that represent amounts in US$. This data starts out life as a pandas.Series. Legible plotting is easy (following assumes jupyter notebook):
p = figure(title='Example currency', x_axis_type='datetime',
plot_height=200, plot_width=600, tools='')
p.line(my_data.index, my_data)
p.yaxis[0].formatter = NumeralTickFormatter(format='$0,0')
show(p)
This shows me the time-series, with date-formatting on the x-axis and y-axis values that look like “
200,000”, “$250,000”, etc. I have two questions about HoverTool behavior:
- Controlling formatting for
$xand$y. - Accessing the name of the dataset under the cursor.
Simply adding aHoverToolallows me to see values, but in unhelpful units:
p.add_tools(HoverTool())
The corresponding tooltip values with these defaults show “1.468e+5” rather than “$146,800” (or even “146800”, the underlying Series value); similarly, the date value appears as “1459728000000” rather than (say) “2016-04-04”. I can manually work around this display issue by making my pandas.Series into a ColumnDataSource and adding string columns with the desired formatting:
# Make sure Series and its index have `name`, before converting to DataFrame
[my_data.name](http://my_data.name) = 'revenue'
[my_data.index.name](http://my_data.index.name) = 'day'
df = my_data.reset_index()
# Add str columns for tooltip display
df['daystr'] = df['day'].dt.strftime('%m %b %Y')
df['revstr'] = df['revenue'].apply(lambda x: '${:,d}'.format(int(x)))
cds = ColumnDataSource(df)
p = figure(title='Example currency', x_axis_type='datetime',
plot_height=200, plot_width=600, tools='')
p.line('day', 'revenue', source=cds)
p.yaxis[0].formatter = NumeralTickFormatter(format='$0,0')
p.add_tools(HoverTool(tooltips=[('Amount', '@revstr'), ('Day', '@daystr')]))
show(p)
but is there a way to handle the formatting in the HoverTool configuration instead? That seems much more desirable than all the data-set transformation that’s required above. I looked through the documentation and (quickly) scanned through the source, and didn’t see anything obvious that would save me from building the “output” columns as above.
Related to that, when I have several lines in a single plot, is there any way for me to access the name (or perhaps legend value) of each line within HoverTool.tooltips? It would be extremely helpful to include something in the tooltip to differentiate which dataset values are coming from, rather than needing to rely on (say) line-color in conjunction with the tool-tip display. For now, I’ve added an additional column to the ColumnDataSource that’s just the string value I want to show; that obviously only works for datasets that include a single measurement column. When multiple lines are sharing an underlying ColumnDataSource, it would be sufficient to access the column-name that’s provided to y.
Thank you for any insights or suggestions.
-mt