Understand sns.heatmap() for Beginners – Seaborn Tutorial

By | August 9, 2021

In python, we can use python seaborn library to draw a heatmap graph. In this tutorial, we will use some examples to show you some tips when using it.

sns.heatmap() syntax

sns.heatmap() is defined as:

seaborn.heatmap(data, *, vmin=None, vmax=None, cmap=None, center=None, robust=False, annot=None, fmt='.2g', annot_kws=None, linewidths=0, linecolor='white', cbar=True, cbar_kws=None, cbar_ax=None, square=False, xticklabels='auto', yticklabels='auto', mask=None, ax=None, **kwargs)

We should notice:

data: it usually be a 2-D numpy array.

cmap: Change the color of heatmap.

annot: False or True. Displaying value or not in heatmap.

Here is an example:

import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns

data = np.random.rand(10, 5)
ax = sns.heatmap(data = data)
plt.show()

Here data is a 2-D array, the shape of which is 10 * 5

Running this code, you will get this graph.

import numpy as np import matplotlib.pyplot as plt import seaborn as sns  data = np.random.rand(10, 5) ax = sns.heatmap(data = data) plt.show()

The shape of data is 10 * 5. From the result, we can find:

row = 10, which is the y axis.

column = 5, which is x axis.

Change the color of heatmap

We can set parameter cmap to implement it.

Here is an example:

import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns

data = np.random.rand(10, 5)
ax = sns.heatmap(data = data, cmap="YlGnBu")
plt.show()

Run this code, you will get this result:

Change the color of heatmap in python

Display value in heatmap

Here is an example:

data = np.random.rand(10, 5)
ax = sns.heatmap(data = data, annot = True)
plt.show()

Run this code, we will get this heatmap.

Display value in heatmap in python seaborn

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