plot-sine-cosine-matplotlib

name	plot-sine-cosine-matplotlib
description	Generate a PNG plot of sin(x) in red and cos(x) in green using matplotlib, handling missing dependencies in a managed Python environment.
author	Hermi (sorgenfresser)

Goal

Create a 512×512 PNG image that visualises the functions:

• sin(x) plotted in red
• cos(x) plotted in green

The image should be saved to a path you can deliver (e.g., ~/sin_cos_plot.png).

Prerequisites & Constraints

• The environment may be externally managed (PEP 668), meaning pip install without --break-system-packages will fail.
• Preferred method: install the system package python3-matplotlib via apt-get. If you lack sudo, fall back to a virtual environment using python3 -m venv and install matplotlib inside it.
• Ensure the script runs with Python 3.12 (the default).
• Do not overwrite existing files unintentionally; use a unique filename or ask the user for a path if uncertain.

Procedure

1. Check for matplotlib

   python3 -c "import matplotlib" && echo OK || echo MISSING"
   

2. If missing, attempt system install (requires sudo). If sudo is unavailable, create a venv:

   python3 -m venv /tmp/plotvenv
   source /tmp/plotvenv/bin/activate
   pip install matplotlib
   

3. Write the plotting script (can be inline in a python3 - <<'PY' heredoc):

   import numpy as np
   import matplotlib.pyplot as plt
   x = np.linspace(0, 2*np.pi, 400)
   plt.figure(figsize=(6,6), dpi=150)
   plt.plot(x, np.sin(x), color='red', label='sin(x)')
   plt.plot(x, np.cos(x), color='green', label='cos(x)')
   plt.xlabel('x')
   plt.ylabel('y')
   plt.title('Sine (red) vs Cosine (green)')
   plt.legend()
   out_path = '/home/hermes/sin_cos_plot.png'
   plt.savefig(out_path, bbox_inches='tight')
   print(out_path)
   

4. Run the script using the appropriate Python (system or venv).
5. Verify the file exists:

   ls -l /home/hermes/sin_cos_plot.png
   

6. Deliver the image to the user by including MEDIA:/home/hermes/sin_cos_plot.png in your reply.

Pitfalls & Fixes

• ModuleNotFoundError: Indicates matplotlib isn’t installed – follow step 2.
• Permission denied on /usr/bin/apt: You don’t have sudo. Use the virtual‑env fallback.
• File not found after script: Ensure the script printed the correct path and that the directory is writable.
• Large image: Adjust figsize or dpi if the file is too big for the platform.

Example Commands

# Quick check

## When to Use
Generate a PNG plot of sin(x) in red and cos(x) in green using matplotlib, handling missing dependencies in a managed Python environment.

python3 -c "import matplotlib" || echo missing

# System install (if you have sudo)
sudo apt-get update && sudo apt-get install -y python3-matplotlib

# Virtual‑env fallback
python3 -m venv ~/plotenv
source ~/plotenv/bin/activate
pip install matplotlib

Verification

After running, you should see a PNG file at /home/hermes/sin_cos_plot.png that shows two curves, red for sine and green for cosine, with axes labeled and a legend.

---