Heatmap

Confusion Matrix Heatmap

Dark theme confusion matrix for ML classification

Output
Confusion Matrix Heatmap
Python
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import LinearSegmentedColormap
from matplotlib.patches import FancyBboxPatch

fig, ax = plt.subplots(figsize=(10, 9), facecolor='#ffffff')
ax.set_facecolor('#ffffff')

np.random.seed(42)
classes = ['Cat', 'Dog', 'Bird', 'Fish', 'Horse']
n = len(classes)
data = np.random.randint(0, 20, (n, n))
np.fill_diagonal(data, np.random.randint(80, 150, n))

colors = ['#1e293b', '#0c4a6e', '#0284c7', '#38bdf8', '#bae6fd']
cmap = LinearSegmentedColormap.from_list('cm', colors, N=256)

cell_w, cell_h = 0.88, 0.88
for i in range(n):
    for j in range(n):
        val = data[i, j]
        rect = FancyBboxPatch((j - cell_w/2, i - cell_h/2), cell_w, cell_h,
                               boxstyle="round,pad=0.02,rounding_size=0.12",
                               facecolor=cmap(val/data.max()), edgecolor='#e2e8f0', linewidth=1.5)
        ax.add_patch(rect)
        ax.text(j, i, str(val), ha='center', va='center', color='#1e293b', fontsize=12, fontweight='bold')

ax.set_xlim(-0.5, n-0.5)
ax.set_ylim(-0.5, n-0.5)
ax.set_aspect('equal')
ax.invert_yaxis()
ax.set_xticks(range(n))
ax.set_yticks(range(n))
ax.set_xticklabels(classes, color='#64748b', fontsize=10, fontweight='500')
ax.set_yticklabels(classes, color='#1e293b', fontsize=10, fontweight='500')

sm = plt.cm.ScalarMappable(cmap=cmap, norm=plt.Normalize(0, data.max()))
cbar = plt.colorbar(sm, ax=ax, shrink=0.8, pad=0.02)
cbar.set_label('Count', color='#1e293b', fontsize=11)
cbar.outline.set_edgecolor('#e2e8f0')
plt.setp(plt.getp(cbar.ax.axes, 'yticklabels'), color='#64748b')

for spine in ax.spines.values(): spine.set_visible(False)
ax.tick_params(length=0)
ax.set_xlabel('Predicted', fontsize=12, color='#64748b', labelpad=10)
ax.set_ylabel('Actual', fontsize=12, color='#64748b', labelpad=10)
ax.set_title('Classification Confusion Matrix', fontsize=18, color='#1e293b', fontweight='bold', pad=20)
plt.tight_layout()
plt.show()
Library

Matplotlib

Category

Heatmaps & Density

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