ngspice-matplotlib-plot

name	ngspice-matplotlib-plot
description	Use when the task is to run an ngspice .cir netlist from the command line and generate waveform plots with matplotlib. Trigger on requests to simulate SPICE files, run ngspice automatically, plot wrdata output, or turn .cir files into waveform images.

ngspice Matplotlib Plot

Use this skill when a task needs to run ngspice on a .cir file and turn the generated wrdata output into a plot.

Environment Requirements

• A Python environment with matplotlib installed.
• ngspice installed and callable as ngspice.
• The bundled script writes matplotlib config and cache data into the current working directory if needed.
• Prefer a project-local .venv when one exists.
• If no project-local environment exists, use a Python interpreter explicitly instead of assuming python resolves correctly.
• Before invoking Python plotting, it is safe to set:

  MPLCONFIGDIR="$(pwd)/.mplconfig"
  XDG_CACHE_HOME="$(pwd)/.cache"
  

Default Workflow

1. Confirm the .cir file contains a wrdata ... line.
2. Choose a Python interpreter:
   • Prefer ./.venv/bin/python if the repo already has one.
   • Otherwise use an explicitly chosen interpreter such as python3.
3. Run the bundled script with that interpreter.
4. By default, let the script delete the generated .dat file after plotting.
5. Use --keep-data only when the user wants to inspect or reuse the raw exported data.

Command Pattern

MPLCONFIGDIR="$(pwd)/.mplconfig" \
XDG_CACHE_HOME="$(pwd)/.cache" \
python3 \
~/.codex/skills/ngspice-matplotlib-plot/scripts/run_ngspice_and_plot.py \
<path-to-netlist.cir> [--output output.png] [--title "Plot Title"] [--keep-data]

Notes

• The script expects wrdata output in the netlist. It parses the file name and expressions from that command.
• The generated image defaults to <netlist_stem>_plot.png in the same directory as the netlist.
• The bundled script uses the non-interactive Agg matplotlib backend, so it works in headless terminal sessions.
• If a collaborator stores skills somewhere other than ~/.codex/skills/, adjust the script path accordingly.