bio-differential-expression-edger-basics

bio-differential-expression-edger-basics is a skill for Claude Code, Codex from GPTomics/bioSkills. It costs 173 tokens per session (5,845 once invoked), scanned A, original, MIT.

A guide to using edgeR, an R package that tests whether gene activity differs between conditions in bulk RNA sequencing data. It covers count filtering, normalization, statistical modelling, and effect-size testing.

In plain words
What is it for?
Use it to analyze bulk RNA-seq count tables, fit models, test contrasts, rank differentially expressed genes, and apply fold-change thresholds.
Why use it?
It provides a consistent way to account for sequencing depth and count variability instead of comparing raw counts directly.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to analyze bulk RNA-seq count tables, fit models, test contrasts, rank differentially expressed genes, and apply fold-change thresholds.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/gptomics/bioskills/edger-basics
Install

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.

Any agent
npx skills add GPTomics/bioSkills --skill edger-basics
Clone the repo
git clone --depth 1 https://github.com/GPTomics/bioSkills

Made for: Claude Code, Codex.

Wrote 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.

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README.md
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Your own site
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Per session 173 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,845 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00173 $0.05845
Opus 5 $0.00086 $0.02923
Sonnet 5 $0.00035 $0.01169
Haiku 4.5 $0.00017 $0.00585

Measured 8d ago against content hash 8657e48c234c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

bio-differential-expression-edger-basics 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 8d 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.

differential-expression/edger-basics/SKILL.md · 311 lines

How it starts

The opening of the file, as written. The whole thing — 311 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Version Compatibility

Reference examples tested with: edgeR 4.0+, limma 3.58+, statmod 1.5+ (for voom internals), tximport 1.30+ (for catchSalmon path)

Before using code patterns, verify installed versions match. If versions differ:

  • R: packageVersion('<pkg>') then ?function_name to verify parameters

If code throws ImportError, AttributeError, or TypeError, introspect the installed package and adapt the example to match the actual API rather than retrying.

edgeR Basics

"Find differentially expressed genes between conditions" -> Fit a negative-binomial GLM per gene with empirical-Bayes-moderated dispersions, test coefficients with the quasi-likelihood F-test (proper finite-sample FPR control), and report ranked DE lists.

The Single Most Important Modern Insight -- edgeR v4 changed the QL framework and legacy=FALSE is now default

Chen, Chen, Lun, Baldoni, Smyth (2025) Nucleic Acids Res 53(2):gkaf018 introduced a bias-corrected adjusted profile likelihood (APL) for dispersion estimation that handles small/zero counts properly, and reworked the QL framework. glmQLFit() in v4 takes legacy=FALSE by default. Old (v3) pipelines that worked perfectly in 2023 now produce subtly different numbers in 2025 -- not wrong, just different. If a tutorial result doesn't match, check which version was used; set legacy=TRUE to reproduce v3 exactly OR (preferred) re-run with v4 defaults and accept the new -- better -- numbers.

Two other v4 changes worth knowing: (1) calcNormFactors() is deprecated in favor of normLibSizes() (same function, new name); (2) method='TMM' remains the documented default; method='TMMwsp' (TMM with singleton pairing) is an alternative introduced for samples with many zeros and is the preferred choice for sparse / low-count data. Pass method= explicitly for reproducibility. Old names still work, so old scripts run, but new code should use the new names.

The choice between Wald-equivalent (glmLRT) and QL-F (glmQLFTest) is not a stylistic preference: glmQLFTest is the modern default because it accounts for uncertainty in the dispersion estimate via an additional QL dispersion. glmLRT is anti-conservative with small n. The two p-values differ -- glmQLFTest p-values are typically >= glmLRT p-values for the same model (the second-stage QL dispersion correction is usually >= 1).

Read the full file on GitHub · 311 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

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.

  1. 8d ago First seen · 311 lines · 173 tokens per session scan A 8657e48c234c

Subscribe to this mod's changes

bio-differential-expression-edger-basics is a skill published in the GitHub repository GPTomics/bioSkills (1,201 stars, last pushed 27d ago), licensed MIT. It adds 173 tokens to every session and 5,845 once invoked, about $0.0009 per session on Opus 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 2026-09-03.

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