# How to Plot a 2D Heatmap With Matplotlib

Suraj Joshi Feb 02, 2024

To plot a 2D heatmap, we can use any of the following methods:

• `imshow()` function with parameters `interpolation='nearest'` and `cmap='hot'`
• `Seaborn` library
• `pcolormesh()` function

## `imshow()` Function to Plot 2D Heatmap

Syntax for we can use the `imshow` function:

``````matplotlib.pyplot.imshow(X,
cmap=None,
norm=None,
aspect=None,
interpolation=None,
alpha=None,
vmin=None,
vmax=None,
origin=None,
extent=None,
shape= < deprecated parameter > ,
filternorm=1,
imlim= < deprecated parameter > ,
resample=None,
url=None,
*,
data=None,
**kwargs)
``````

Example Codes:

``````import numpy as np
import matplotlib.pyplot as plt

data = np.random.random((8, 8))
plt.imshow(data, cmap="cool", interpolation="nearest")
plt.show()
``````

`cmap` is color map and we can choose another built-in `colormaps` too from here.

`interpolation` is the interpolation method that could be `nearest`, `bilinear`, `hamming`, etc.

## 2D Heatmap With `Seaborn` Library

The `Seaborn` library is built on top of Matplotlib. We could use `seaborn.heatmap()` function to create 2D heatmap.

``````import numpy as np
import seaborn as sns
import matplotlib.pylab as plt

data = np.random.rand(8, 8)
ax = sns.heatmap(data, linewidth=0.3)
plt.show()
``````

Seaborn also plots a gradient at the side of the `heatmap`.

## `pcolormesh()` Function

Another way to plot 2D heatmap is using `pcolormesh()` function ,which creates a pseudo-color plot with a non-regular rectangular grid. It is a faster alternative to `pcolor()` function.

``````import numpy as np
import matplotlib.pyplot as plt

b, a = np.meshgrid(np.linspace(0, 5, 130), np.linspace(0, 5, 130))

c = (a ** 2 + b ** 2) * np.exp(-(a ** 2) - b ** 2)
c = c[:-1, :-1]
l_a = a.min()
r_a = a.max()
l_b = b.min()
r_b = b.max()
l_c, r_c = -np.abs(c).max(), np.abs(c).max()

figure, axes = plt.subplots()

c = axes.pcolormesh(a, b, c, cmap="copper", vmin=l_c, vmax=r_c)
axes.set_title("Heatmap")
axes.axis([l_a, r_a, l_b, r_b])
figure.colorbar(c)

plt.show()
``````

Output:

Author: Suraj Joshi

Suraj Joshi is a backend software engineer at Matrice.ai.