# How to create a box (and whisker) plot (in Python, using Matplotlib)

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A box plot, or a box and whisker plot, shows the quartiles of a single variable from a dataset (one of which is the median) and may also show the outliers. It is a simplified way to see the distribution of a variable. Sometimes multiple box plots (one for each of several variables) are shown side-by-side on a plot, to compare the variables. How can we create such graphs?

## Solution

We will create some fake data using Python lists, for simplicity. But everything we show below works also if your data is in columns of a DataFrame, such as df['age'].

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patient_id     = [   0,   1,   2,   3,   4,   5,   6,   7,   8,   9 ]
patient_height = [  60,  64,  64,  65,  66,  66,  70,  72,  72,  76 ]
patient_weight = [ 141, 182, 169, 204, 138, 198, 180, 175, 244, 196 ]


The conventional way to import matplotlib in Python is as follows.

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import matplotlib.pyplot as plt


To create a box-and-whisker plot, sometimes called just a box plot requires just one line of code, plus one to show the plot.

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plt.boxplot( patient_height )
plt.show()


You can show more than one variable’s box plot side-by-side by forming a list of the data.

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plt.boxplot( [ patient_height, patient_weight ] )
plt.show()