[Matplotlib-users] boxplot behaviour in an extreme scenario

[chtan <ch...@un...>]

Hi,

the outliers in the boxplot do not seem to be drawn in the following extreme
scenario:
Data Value: 1, Frequency: 5
Data Value: 2, Frequency: 100
Data Value: 3, Frequency: 5

Here, Q1 = Q2 = Q3, so IQR = 0.
Data values 1 and 3 are therefore outliers according to the definition in
the api
(Refer to parameter "whis" under "boxplot": 
http://matplotlib.org/api/pyplot_api.html
<http://matplotlib.org/api/pyplot_api.html>  )

But the code below produces a boxplot that shows them as max-min whiskers
(rather than fliers):

import matplotlib.pyplot as plt
data = 100 * [2] + 5 * [1] + 5 * [3]
ax = plt.gca()
bp = ax.boxplot(data, showfliers=True)
for flier in bp['fliers']:
    flier.set(marker='o', color='gray')

<http://matplotlib.1069221.n5.nabble.com/file/n46027/figure_1.png> 


What I though it would look like is obtained by perturbing half of the data
points 2 to 2.000001:

<http://matplotlib.1069221.n5.nabble.com/file/n46027/figure_2.png> 


Is this a bug or I'm not getting something right?

rgds
marcus



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