🔥 Seaborn Heatmap

Last Updated: 07 Nov 2025

A heatmap visualizes data in a matrix form where values are represented using colors. Most commonly used for:

  • Correlation matrix
  • Pivot tables

Hinglish Tip 🗣: Heatmap me color hi value hota hai — darker/lighter color = high/low value.

Basic Syntax

sns.heatmap(data)
plt.show()

📘 Example Dataset

df = sns.load_dataset('tips')

We will create a correlation matrix first:

corr = df.corr(numeric_only=True)

🔥 Basic Heatmap

sns.heatmap(corr)
plt.show()

Important Parameters

  • annot Shows values on heatmap.
sns.heatmap(corr, annot=True)
plt.show()
  • fmt Format of annotation numbers.
sns.heatmap(corr, annot=True, fmt='.2f')
  • cmap Color palette. Popular options: magma, viridis, crest, rocket
sns.heatmap(corr, cmap='coolwarm')
  • linewidths Lines between cells.
sns.heatmap(corr, linewidths=1)
  • linecolor Color of grid lines.
sns.heatmap(corr, linewidths=1, linecolor='white')
  • square Make cells perfect squares.
sns.heatmap(corr, square=True)
  • cbar Show/hide color bar.
sns.heatmap(corr, cbar=False)
  • cbar_kws Customize color bar.
sns.heatmap(corr, cbar_kws={'shrink':0.5})
  • mask Hide specific parts of heatmap. Example: show only upper triangle.
import numpy as np
mask = np.triu(np.ones_like(corr))
sns.heatmap(corr, mask=mask)

⭐ Full Example

sns.heatmap(
    corr,
    annot=True,
    fmt='.2f',
    cmap='viridis',
    linewidths=0.8,
    linecolor='white',
    square=True,
    cbar_kws={'shrink': 0.6}
)
plt.show()

Quick Practice

  1. Load penguins dataset.
  2. Compute correlation matrix.
  3. Plot heatmap with annot=True.
  4. Change colormap.
  5. Show only upper triangle using mask.
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