How to create a seaborn.heatmap() with frames around the tiles?

To create frames around the tiles in a Seaborn heatmap, we can use the linewidths and linecolor parameters in the heatmap() method. This adds visual separation between cells, making the data more readable.

Basic Syntax

sns.heatmap(data, linewidths=width, linecolor='color')

Parameters

• linewidths − Width of the lines that will divide each cell (float)
• linecolor − Color of the lines that will divide each cell (string or RGB)

Example with Green Frames

Here's how to create a heatmap with green frames around each tile −

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

# Set figure size
plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

# Create sample data
df = pd.DataFrame(np.random.random((5, 5)), 
                  columns=["col1", "col2", "col3", "col4", "col5"])

# Create heatmap with green frames
sns.heatmap(df, linewidths=4, linecolor='green')

plt.show()

Different Frame Styles

You can customize the appearance with different colors and widths −

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

# Create sample data
data = np.random.randint(1, 100, (4, 4))
df = pd.DataFrame(data, columns=['A', 'B', 'C', 'D'])

# Create subplots for comparison
fig, axes = plt.subplots(1, 3, figsize=(15, 4))

# Thin white lines
sns.heatmap(df, linewidths=0.5, linecolor='white', ax=axes[0])
axes[0].set_title('Thin White Lines')

# Medium black lines
sns.heatmap(df, linewidths=2, linecolor='black', ax=axes[1])
axes[1].set_title('Medium Black Lines')

# Thick red lines
sns.heatmap(df, linewidths=3, linecolor='red', ax=axes[2])
axes[2].set_title('Thick Red Lines')

plt.tight_layout()
plt.show()

Comparison Table

Conclusion

Use linewidths and linecolor parameters to add frames around heatmap tiles. Choose appropriate width values based on your visualization needs − thin lines for subtle separation, thicker lines for bold emphasis.