Nytaxi Hover#
Download this script from GitHub (right-click to download).
"""
Bokeh app example using datashader for rasterizing a large dataset and
geoviews for reprojecting coordinate systems.
This example requires the 1.7GB nyc_taxi_wide.parquet dataset which
you can obtain by downloading the file from AWS:
https://s3.amazonaws.com/datashader-data/nyc_taxi_wide.parq
Place this parquet in a data/ subfolder and install the python dependencies, e.g.
conda install datashader fastparquet python-snappy
You can now run this app with:
bokeh serve --show nytaxi_hover.py
"""
import dask.dataframe as dd
import numpy as np
import holoviews as hv
from holoviews import opts
from holoviews.operation.datashader import aggregate
hv.extension("bokeh")
renderer = hv.renderer("bokeh")
# Set plot and style options
opts.defaults(
opts.Curve(
xaxis=None,
yaxis=None,
show_grid=False,
show_frame=False,
color="orangered",
framewise=True,
width=100,
),
opts.Image(
width=800,
height=400,
shared_axes=False,
logz=True,
colorbar=True,
xaxis=None,
yaxis=None,
axiswise=True,
bgcolor="black",
),
opts.HLine(color="white", line_width=1),
opts.Layout(shared_axes=False),
opts.VLine(color="white", line_width=1),
)
# Read the parquet file
df = dd.read_parquet("./data/nyc_taxi_wide.parq").persist()
# Declare points
points = hv.Points(df, kdims=["pickup_x", "pickup_y"], vdims=[])
# Use datashader to rasterize and linked streams for interactivity
agg = aggregate(points, link_inputs=True, x_sampling=0.0001, y_sampling=0.0001)
pointerx = hv.streams.PointerX(x=np.mean(points.range("pickup_x")), source=points)
pointery = hv.streams.PointerY(y=np.mean(points.range("pickup_y")), source=points)
vline = hv.DynamicMap(hv.VLine, streams=[pointerx])
hline = hv.DynamicMap(hv.HLine, streams=[pointery])
sampled = hv.util.Dynamic(
agg, operation=lambda obj, x: obj.sample(pickup_x=x), streams=[pointerx], link_inputs=False
)
hvobj = (agg * hline * vline) << sampled
# Obtain Bokeh document and set the title
doc = renderer.server_doc(hvobj)
doc.title = "NYC Taxi Crosshair"
