choropleth plotly map displaying a white background - plotly-python

Question

I am trying to create a choropleth map of the uk using plotly, but every time I try, it outputs an empty page, or the json doesn't match with the dataframe.this is where i obtained the url for the dataframe Here's my code so far:
import pandas as pd
from urllib.request import urlopen
import json
with urlopen('https://raw.githubusercontent.com/deldersveld/topojson/master/countries/united-kingdom/uk-counties.json') as response:
geojson = json.load(response)
url3 = 'https://api.coronavirus.data.gov.uk/v2/data?areaType=utla&metric=cumCasesBySpecimenDate&metric=cumPeopleVaccinatedFirstDoseByVaccinationDate&metric=cumPeopleVaccinatedSecondDoseByVaccinationDate&metric=newCasesBySpecimenDate&metric=cumPeopleVaccinatedThirdInjectionByVaccinationDate&format=csv'
df = pd.read_csv(url3)
df_new=df.replace("areaName", "NAME_2")
from plotly import graph_objects as go
fig = go.Figure(
go.Choroplethmapbox(
geojson=geojson,
featureidkey="properties.NAME_2",
locations=df["areaCode"],
z=df['cumCasesBySpecimenDate'],
zauto=True,
colorscale='Reds',
showscale=True,
)
)
fig.show()

Answer 1

a few things to fix this up:
uk-counties.json is in topojson format, plotly needs a geojson. can fix with the topojson module, for example (or geopandas)
no need to replace "areaName", you want this: locations=df["areaName"]
you need to specify a marker_style. centering and zooming help as well
for good result you need to use only one day's worth of data per choropleth, hence the df = df[df['date'] == '2022-11-23']
the covid data and the topojson don't match up well by districts, so there are gaps in the map
code:
"""
https://stackoverflow.com/questions/71828342/choropleth-plotly-map-displaying-a-white-background
"""
from urllib.request import urlretrieve
import json
from io import StringIO
from plotly import graph_objects as go
import pandas as pd
import topojson as tp
URL_JSON = 'https://raw.githubusercontent.com/deldersveld/topojson/master/countries/united-kingdom/uk-counties.json'
URL_DATA = 'https://api.coronavirus.data.gov.uk/v2/data?areaType=utla&metric=cumCasesBySpecimenDate&metric=cumPeopleVaccinatedFirstDoseByVaccinationDate&metric=cumPeopleVaccinatedSecondDoseByVaccinationDate&metric=newCasesBySpecimenDate&metric=cumPeopleVaccinatedThirdInjectionByVaccinationDate&format=csv'
CSV_DATA = 'uk_covid.csv'
TOPO_DATA = 'topojson.json'
GEO_DATA = 'geojson.json'
def download():
urlretrieve(URL_JSON, TOPO_DATA)
with open(TOPO_DATA, 'r') as data:
topoJSON = json.load(StringIO(data.read()))
topo = tp.Topology(topoJSON, object_name='GBR_adm2')
# convert to geojson, store in GEO_DATA
topo.to_geojson(GEO_DATA)
df = pd.read_csv(URL_DATA)
df.to_csv(CSV_DATA)
def make_map():
df = pd.read_csv(CSV_DATA)
with open(GEO_DATA, 'r') as data:
geojson = json.load(StringIO(data.read()))
# one day at a time
df = df[df['date'] == '2022-11-23']
fig = go.Figure(
go.Choroplethmapbox(
geojson=geojson,
featureidkey="properties.NAME_2",
locations=df["areaName"], # <=== not areaCode
z=df['cumCasesBySpecimenDate'],
zauto=True,
colorscale='Reds',
showscale=True
)
)
# need a mapbox_style
fig.update_layout(mapbox_style='carto-positron',
mapbox_zoom=5,
mapbox_center_lon=-2.057852,
mapbox_center_lat=53.404854,
height=700,
width=700)
fig.show()
if 0: # only needed once
download()
make_map()