Panel dashboard#

hvplotbokehdatashaderpanelparamdask

Published: January 29, 2016 · Modified: August 20, 2024

The NYC Taxi trips dataset is a well-studied data science example. Here we show how to build a simple dashboard for exploring 10 million taxi trips in a Jupyter notebook using Datashader, then deploying it as a standalone dashboard using Panel.

import holoviews as hv
import param
import dask.dataframe as dd
import panel as pn

from holoviews.operation.datashader import rasterize, dynspread
from holoviews.element.tiles import EsriStreet

hv.extension('bokeh')

usecols = ['dropoff_x', 'dropoff_y', 'pickup_x', 'pickup_y', 'dropoff_hour', 'pickup_hour', 'passenger_count']
df = dd.read_parquet('data/nyc_taxi_wide.parq', engine='fastparquet')[usecols].persist()
opts = dict(width=1000, height=600, xaxis=None, yaxis=None, bgcolor='black', show_grid=False)
cmaps = ['fire', 'bgy', 'bgyw', 'bmy', 'gray', 'kbc']

df.head()

	dropoff_x	dropoff_y	pickup_x	pickup_y	dropoff_hour	pickup_hour	passenger_count
0	-8234835.5	4975627.0	-8236963.0	4975552.5	19	19	1
1	-8237020.5	4976875.0	-8237826.0	4971752.5	20	20	1
2	-8232279.0	4986477.0	-8233561.5	4983296.5	20	20	1
3	-8238124.0	4971127.0	-8238654.0	4970221.0	20	20	1
4	-8238107.5	4974457.0	-8234433.5	4977363.0	20	20	1

class NYCTaxiExplorer(pn.viewable.Viewer):
    alpha      = param.Magnitude(default=0.75, doc="Alpha value for the map opacity")
    cmap       = param.Selector(objects=cmaps)
    hour       = param.Range(default=(0, 24), bounds=(0, 24))
    location   = param.Selector(objects=['dropoff', 'pickup'])

    @param.depends('location', 'hour')
    def points(self):
        points = hv.Points(df, kdims=[self.location+'_x', self.location+'_y'], vdims=['dropoff_hour'])
        if self.hour != (0, 24):
            points = points.select(dropoff_hour=self.hour)
        return points

    def __panel__(self, **kwargs):
        points = hv.DynamicMap(self.points)
        tiles = EsriStreet().apply.opts(alpha=self.param.alpha, **opts)
        agg = rasterize(points, width=600, height=400).opts(cnorm='eq_hist', nodata=0)
        return tiles * dynspread(agg).apply.opts(cmap=self.param.cmap)
        
taxi = NYCTaxiExplorer(name="NYC Taxi Trips")
pn.Row(taxi.param, taxi).servable()