Polydraw

Title
PolyDraw
Description
A linked streams example demonstrating how to use the PolyDraw stream.
Backends
Bokeh
Tags
streams, linked, position, interactive
In [ ]:
import numpy as np
import holoviews as hv
from holoviews import streams
from matplotlib.path import Path

hv.extension('bokeh')

The PolyDraw stream adds a bokeh tool to the source plot, which allows drawing, dragging and deleting polygons and making the drawn data available to Python. The tool supports the following actions:

Add patch/multi-line

Double tap to add the first vertex, then use tap to add each subsequent vertex, to finalize the draw action double tap to insert the final vertex or press the ESC key to stop drawing.

Move patch/multi-line

Tap and drag an existing patch/multi-line, the point will be dropped once you let go of the mouse button.

Delete patch/multi-line

Tap a patch/multi-line to select it then press BACKSPACE key while the mouse is within the plot area.

As a simple example we will create simple Path and Polygons elements and attach each to a PolyDraw stream. We will also enable the drag option on the stream to enable dragging of existing glyphs.

In [ ]:
%%opts Path [width=400 height=400] (line_width=5 color='red') Polygons (fill_alpha=0.3)
path = hv.Path([[(1, 5), (9, 5)]])
poly = hv.Polygons([[(2, 2), (5, 8), (8, 2)]])
path_stream = streams.PolyDraw(source=path, drag=True)
poly_stream = streams.PolyDraw(source=poly, drag=True)
path * poly

Whenever the data source is edited the data is synced with Python, both in the notebook and when deployed on the bokeh server. The data is made available as a dictionary of columns:

In [ ]:
path_stream.data

Alternatively we can use the element property to get an Element containing the returned data:

In [ ]:
path_stream.element * poly_stream.element

Download this notebook from GitHub (right-click to download).