How do I fill a region with only hatch (no background colour) in matplotlib 2.0?

To fill a region with only hatch patterns and no background color in matplotlib, you need to set specific parameters in the fill_between() function. The key is using facecolor="none" to remove the background fill while keeping the hatch pattern visible.

Basic Syntax

The essential parameters for hatching without background color are ?

ax.fill_between(x, y, facecolor="none", hatch="pattern", edgecolor="color")

Complete Example

Here's how to create a hatched region with no background fill ?

import numpy as np
import matplotlib.pyplot as plt

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

# Number of sample data
n = 256

# x and y data points
x = np.linspace(-np.pi, np.pi, n, endpoint=True)
y = np.sin(2 * x)

# Create figure and subplot
fig, ax = plt.subplots()

# Plot the data line
ax.plot(x, y, color='blue', alpha=1.0)

# Fill area with hatch only (no background color)
ax.fill_between(x, y, facecolor="none", hatch="o", edgecolor="blue", linewidth=1.0)

# Display the plot
plt.show()

Different Hatch Patterns

Matplotlib supports various hatch patterns that you can use ?

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 4, 100)
y1 = np.sin(x)
y2 = np.cos(x)

fig, axes = plt.subplots(2, 2, figsize=(10, 8))
fig.suptitle('Different Hatch Patterns (No Background)')

# Diagonal lines pattern
axes[0,0].fill_between(x, y1, facecolor="none", hatch="///", edgecolor="red")
axes[0,0].plot(x, y1, color='red')
axes[0,0].set_title('Diagonal Lines (///)')

# Dots pattern
axes[0,1].fill_between(x, y2, facecolor="none", hatch="...", edgecolor="green")
axes[0,1].plot(x, y2, color='green')
axes[0,1].set_title('Dots (...)')

# Cross pattern
axes[1,0].fill_between(x, y1, facecolor="none", hatch="xxx", edgecolor="orange")
axes[1,0].plot(x, y1, color='orange')
axes[1,0].set_title('Crosses (xxx)')

# Stars pattern
axes[1,1].fill_between(x, y2, facecolor="none", hatch="***", edgecolor="purple")
axes[1,1].plot(x, y2, color='purple')
axes[1,1].set_title('Stars (***)')

plt.tight_layout()
plt.show()

Key Parameters

Common Hatch Patterns

• / - Forward diagonal lines
• \ - Backward diagonal lines
• | - Vertical lines
• - - Horizontal lines
• + - Crosses
• x - X pattern
• o - Circles
• O - Large circles
• . - Dots
• * - Stars

Conclusion

Use facecolor="none" with hatch parameter to create patterns without background fill. The edgecolor controls the hatch color, while linewidth adjusts the pattern thickness for better visibility.