hover.tooltip convenience function for 'datetime' info

[ijstokes]

It would be nice to make it easy to create a "hover" tooltip template that could do some simple conversions/formatting on "standard" data point information: x, y, size, color, etc. Maybe also some convenience conversions for source attributes of data points.

My particular scenario has to do with providing a hover tooltip which displays a human-readable time stamp for the data point. The x-axis is configured as datetime, but when I display $x I get back a float (seconds since the epoch) which isn't very readable. To get around this, I need to add a ColumnDataSource with a single field, like so:

source = ColumnDataSource(data=dict(
    time=df.map(lambda x: x.strftime('%d-%m-%Y'))
))

and then I tell my tooltip to display ("time", "@time"). This is workable, but it would be nicer if I could just do:

("time", "`stftime('%m-%d-%Y', $x)`"

or something similar to say "do a client-side conversion of $x into something more human-readable"

[damianavila]

It is a nice idea... I heard a lot of weird and funny thing with date handling and formatting in the js side... but I suppose we could try...

[bryevdv]

@damianavila we have a sprintf library on the JS side, we can probably just pass an optional format string directly to it.

[mattpap]

Preliminary support for number and time formatting was added in PR #1484. Thought, no support for date formatting yet.

[drorata]

This is a great addition! Thanks! Could someone add some snippets explaining how to use this?

I got so far:

hover.tooltips = {"x":"$x{int}", "y":"$y{int}"}

will format the values as integers.

Assuming that x is a timestamp-integer, it would be really nice to be able to format it into a date-time.

[steve98654]

I second this feature request. Including additional formatting options for other datatypes would be nice as well (perhaps use formatting options similar to those that a DataTable has?)

[Rakeshbart]

Yes this feature would be really helpful as I have many plots with datetime as the x axis. could you please explain how to use this as well.

[davideuler]

I create the DataSource for human readable datetime like this, and then pass the datasource to glyphs.

def create_data_source(data_frame):
    return ColumnDataSource(
        data=dict(
            date=[x.strftime("%Y-%m-%d") for x in data_frame['date']],
            open=data_frame['open'],
            close=data_frame['close'],
        )
    )

df_inc = df[df.close > df.open]  # get the subset of data frame whose close is bigger than open.
source_inc = create_data_source(df_inc)

p.rect(df.date[inc], mids[inc], w, spans[inc], fill_color="#F2583E", line_color="black",source=source_inc)

[esvhd]

I also support adding this feature, will be very helpful. My hack right now is to create a column of strings representing the dates in my data frame passed in as source and refer to that column in the tooltip..

[adriantorrie]

This feature would be great to have!

Perhaps intially having the ISO 8601 standard covered first with the simple notation of:

• $x{date-time} -> output: 'YYYY-MM-DD HH:MM:SS.[fractional seconds]'
• $x{date} -> output: 'YYYY-MM-DD'
• $x{time} -> output: 'HH:MM:SS.[fractional seconds]'

The actual format of ISO 8601 timestamp has a 'T' or 't' between the date and time parts, e.g ``'YYYY-MM-DDTHH:MM:SS.[fractional seconds]'`, however I've replaced the 'T' with a space character to be human readable. This is acceptable according to RFC3339 in section 5.6 Internet and Date/Time Format:

NOTE: ISO 8601 defines date and time separated by "T".
Applications using this syntax may choose, for the sake of
readability, to specify a full-date and full-time separated by
(say) a space character.

Further examples of international agreed standards are found in RFC3339. Note tough that RFC3339 has the following:

The following is an attempt to create a formal
grammar from ISO 8601. This is informational only and may contain
errors. ISO 8601 remains the authoritative reference.

The above gives a grammar for format names, some examples for discussion are (their are many more in the RFC document above):

• date-month -> usage: $x{date-month} -> output: 01-12
• date-mday
• time-hour
• time-offset

[AlJohri]

@mattpap you mentioned the preliminary support for number and time formatting is done - how does one use the time formatting? I only got as far as @drorata with "$x{int}"