Creating a Boxplot with Matplotlib

Question

I am using python 3 and jupyter notebook. I have a pandas dataframe that is structured like this:

          location  price
Apr 25   ASHEVILLE   15.0
Apr 25   ASHEVILLE   45.0
Apr 25   ASHEVILLE   50.0
Apr 25   ASHEVILLE  120.0
Apr 25   ASHEVILLE  300.0
<class 'pandas.core.frame.DataFrame'>

I am simply trying to create a boxplot for each location to show the range of prices among items in each location.

When I ran the following code:

import matplotlib.pyplot as plt
import numpy as np
%matplotlib inline


plt.boxplot(postings)
plt.show()

It returned TypeError: unhashable type: 'slice'

are you sure postings is a dataframe? try just passing the values of the column and not the whole dataframe. — Paul H
– Paul H, Commented May 22, 2017 at 18:32
It is a df. When I try to pass plt.boxplot(postings.location) instead, it outputs IndexError: 0 — Keenan Burke-Pitts
– Keenan Burke-Pitts, Commented May 22, 2017 at 18:43

Amey Dahale · Accepted Answer · 2017-05-22 19:30:37Z

13

I guess you require boxplot for each location in same graph. I modified given dataframe to add sample data for another location which looks like-

   date   location month  price
0    25  ASHEVILLE   Apr   15.0
1    25  ASHEVILLE   Apr   45.0
2    25  ASHEVILLE   Apr   50.0
3    25  ASHEVILLE   Apr  120.0
4    25  ASHEVILLE   Apr  300.0
5    25  NASHVILLE   Apr   34.0
6    25  NASHVILLE   Apr   55.0
7    25  NASHVILLE   Apr   70.0
8    25  NASHVILLE   Apr  105.0
9    25  NASHVILLE   Apr   85.0

Now, just call boxplot on this frame and provide parameters- column and by

postings.boxplot(column='price', by='location')

answered May 22, 2017 at 19:30

Amey Dahale

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Comments

ImportanceOfBeingErnest · Accepted Answer · 2017-05-22 19:05:28Z

3

I guess "price" is the column of data that you want to have boxplotted. So you need to first select this column and supply only that column to plt.boxplot.

u = u"""index,location,price
    Apr 25,ASHEVILLE,15.0
    Apr 25,ASHEVILLE,45.0
    Apr 25,ASHEVILLE,50.0
    Apr 25,ASHEVILLE,120.0
    Apr 25,ASHEVILLE,300.0"""

import io
import pandas as pd
import matplotlib.pyplot as plt

data = io.StringIO(u)

df = pd.read_csv(data, sep=",", index_col=0)

plt.boxplot(df["price"])
plt.show()

answered May 22, 2017 at 19:05

ImportanceOfBeingErnest

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Comments

fbence · Accepted Answer · 2017-05-22 19:00:03Z

1

Juding from the data, you want to have a boxplot with a single box from the 5 price values you have. You need to pass the actual data you want to make the boxplot from.

plt.boxplot(postings["price"])

Check out the examples here.

answered May 22, 2017 at 19:00

fbence

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