pandas and matplotlib plot dataframe

Question

I have the following pandas dataframe

test = pd.DataFrame({'cities':['A','B','A','B','A','B',],
               'date':['2016-9-1','2016-9-1','2016-9-2','2016-9-2','2016-9-3','2016-9-3'],
               'count':[10,20,30,40,50,60]})

And I'd like to plot two scatter plots, one for city 'A' and one for city 'B'. In each plot, x-axis is date, and y-axis is count.

I tried a bit, but the code is so ugly that I am shy from posting it up. Would appreciate somebody to help with some elegant way to do this.

Thank you.

Don't be shy and show us: nothing is uglier than asking for code without sharing its own — Zeugma
– Zeugma, Commented Sep 6, 2016 at 4:32

piRSquared · Accepted Answer · 2016-09-06 05:03:31Z

1

Setup

test = pd.DataFrame({'cities':['A','B','A','B','A','B',],
               'date':['2016-9-1','2016-9-1','2016-9-2','2016-9-2','2016-9-3','2016-9-3'],
               'count':[10,20,30,40,50,60]})

test.date = pd.to_datetime(test.date)

Solution

import matplotlib.pyplot as plt


gb = test.groupby('cities')

fig, axes = plt.subplots(gb.ngroups)
for i, (name, df) in enumerate(gb):
    ax = axes[i]
    ax.scatter(df['date'].values, df['count'].values)
    ax.set_title(name)

fig.autofmt_xdate()
fig.tight_layout()

edited Sep 6, 2016 at 5:03

answered Sep 6, 2016 at 4:54

piRSquared

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3 Comments

Anton Protopopov Over a year ago

I think you first need to convert date column to datetime with pd.to_datetime because without that it causes an error with plotting.

piRSquared Over a year ago

@AntonProtopopov I do! I forgot that part of the copy/paste... thx

Khris Over a year ago

I'm trying this testA=test[test.cities=='A'] and then testA.plot(x=testA['date'],y=testA['count'],kind='scatter') and I'm getting this error:

KeyError: "['2016-09-01T00:00:00.000000000' '2016-09-02T00:00:00.000000000'\n '2016-09-03T00:00:00.000000000'] not in index"

. Can you explain to me what I'm doing wrong here?

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