Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add spedas/spedas_agent_kit --skill hodogramgit clone --depth 1 https://github.com/spedas/spedas_agent_kitWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/spedas/spedas_agent_kit/hodogram)<a href="https://agentmods.dev/skills/spedas/spedas_agent_kit/hodogram"><img src="https://agentmods.dev/badge/skills/spedas/spedas_agent_kit/hodogram/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/spedas/spedas_agent_kit/hodogram"><img src="https://agentmods.dev/badge/skills/spedas/spedas_agent_kit/hodogram.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00085 | $0.01478 |
| Opus 5.5 | $0.00034 | $0.00591 |
| Sonnet 5.5 | $0.00017 | $0.00296 |
| Haiku 4.5 | $0.00009 | $0.00148 |
Grade A, and why
hodogram scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 67 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Hodogram: component-vs-component polarization plot
A hodogram plots one vector component against another (e.g. B in the maximum- vs
intermediate-variance direction) as a parametric curve traced over time. Its shape
reveals polarization — a line (linear), a circle (circular), an ellipse (elliptical) —
and the direction the curve is traced gives the rotation sense. It is the standard
companion to minimum-variance analysis (MVA) for classifying waves and characterizing
boundary rotations (e.g. magnetopause/current-sheet field rotation). This skill composes
existing tools — render_tplot gained scatter/x-y panels (#120/#123), so no new tool is added.
When to use
- "Plot the hodogram of B for this interval" / "is this fluctuation linear, circular, or elliptical?"
- "Which way does B rotate across this boundary?" (rotation sense / handedness).
- The polarization companion to
boundary-minimum-variance— view B_max vs B_int in the LMN frame.
Tool chain (all already exist)
create_spedas_analysis_bundle → fetch_data_product (B vector) →
(analyze_minvar_coordinates to get the LMN/variance frame, recommended) →
transform_timeseries_coordinates or the MVA-rotated series → write one .npz
matrix of the two components → render_tplot(panel_types=["scatter"], x_component, y_component).
Backend (VERIFIED contract)
The hodogram is produced by render_tplot's scatter/x-y panel (added in #123):
render_tplot(input_files=[npz], output_file=..., panel_types=["scatter"], x_component=[i], y_component=[j], ...)renders one 2-D matrix per.npzas a parametric x-y plot of columnivs columnj(defaults 0 vs 1).panel_typesmay also use"xy"; it overrides the per-file default.x_component/y_componentare lists of column indices, one per input file. Mismatched lengths return a structuredinvalid_argumenterror (validated before any drawing).- One matrix per file: to plot B_max-vs-B_int and B_max-vs-B_min as two panels, write
two
.npzinputs (or pass the same file twice with differentx_component/y_component), not one multi-key file expecting a multi-panel stack. - Input
.npzholds the vector as an N×kdatamatrix (component columns) and atimeaxis; the scatter panel ignorestimefor positioning but uses the row order to trace the curve. - Verified live: a 2-column circular series rendered with
panel_types=["scatter"], x_component=[0], y_component=[1]returnsstatus: successand writes a PNG.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 67 lines · 85 tokens per session scan A e9ee92ba9e8e
hodogram is a skill published in the GitHub repository spedas/spedas_agent_kit (3 stars, last pushed 2mo ago), licensed MIT. It adds 85 tokens to every session and 1,478 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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