Why does PyPlot change plot types after I reorganize my data?

Hi all, I seem to be having some issues plotting a map. Please bear with me, as I am new to this.

I’d like to take some company sales data and make a choropleth (and eventually a bubble map) to show which counties in Ireland are our most active in terms of sales. I am able to merge the shapefiles for the Republic of Ireland and Northern Ireland into one dataset so that I capture sales across our fair island, but my issue stems from the fact that I have more than one data point for some counties.

When I try to plot ireland_sales with the Volume column, I get this:

Happy days! However, when I try to consolidate my data to just one point per county using a groupby sum and then a merge, plotting ireland_sales_summed with the County Volume Total column gets me a nearly imperceptible line graph instead of a map:

My data for ireland_sales and ireland_sales_summed look like this:

My code is below. Thanks in advance for the help!

import pandas as pd
import geopandas as gpd
import matplotlib.pyplot as plt

#read shapefiles

ni = gpd.read_file(#shapefile_path)
republic = gpd.read_file(#shapefile_path)

#create NI centroids

ni['centroid'] = ni['geometry'].centroid

#convert NI centroids to x/y to match Republic shapefile

ni['centroid'] = ni['centroid'].astype(str)
ni['centroid'] = ni.apply(lambda x: x['centroid'][7:-1], axis=1)
ni[['CENTROID_X','CENTROID_Y']] = ni['centroid'].str.split(' ', expand=True)
ni = ni.drop(['centroid'], axis=1)

#bring shapefiles into common coordinate system

ni = ni.to_crs('EPSG:4326')
republic = republic.to_crs('EPSG:4326')

#merge shapefiles
ireland = gpd.pd.concat([republic, ni])
counties = []
for i in ireland['COUNTY']:
    if type(i) == str:
        counties.append(i)
for i in ireland['CountyName']:
    if type(i) == str:
        counties.append(i)
ireland['County'] = counties
ireland = ireland.drop(['COUNTY', 'CountyName','ENGLISH', 'GAEILGE', 'CONTAE', 'PROVINCE', 'OBJECTID'], axis=1)

#read in and process data

sales = pd.read_csv(#data_path)

ireland_sales = ireland.merge(sales, on='County')
ireland = ireland[~ireland['County'].isin(sales['County'])]
ireland_sales = pd.concat([ireland_sales, ireland])
ireland_sales['Volume'] = ireland_sales['Volume'].fillna(0)

ireland_vol_total = ireland_sales.groupby('County').sum(numeric_only=True)
ireland_vol_total = ireland_vol_total.drop(['AREA'], axis=1)
ireland_vol_total = ireland_vol_total.rename(columns={'Volume':'County Volume Total'})

ireland_sales_summed = ireland_vol_total.merge(ireland_sales, on='County')
ireland_sales_summed = ireland_sales_summed.drop(['Customer', 'Volume'], axis=1)
ireland_sales_summed = ireland_sales_summed.drop_duplicates(subset=['County'],keep='first')

#plot data

fig, ax = plt.subplots(1, 1)
fig.set_size_inches(10,10)

#produces map
ireland_sales.plot(ax=ax, column='Volume', cmap='Blues')

#produces line chart?
ireland_sales_summed.plot(ax=ax, column='County Volume Total', cmap='Blues')

ax.set_axis_off()

plt.show()

I think this is a geopandas question rather than a matplotlib question as you are not using matplotlib’s plotting functions directly. pyplot.plot could not produce anything like your first example. It looks like StackOverflow and StackExchange are the recommended places for geopandas questions.