Heatmap
Confusion Matrix Heatmap
Dark theme confusion matrix for ML classification
Output
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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