Matlab

---
name: matlab
description: Designs, reviews, and migrates MATLAB R2026a and GNU Octave numerical code, covering functions with arguments blocks, arrays and indexing, tables and timetables, matlab.unittest tests, MATLAB Projects, exportgraphics figures, MAT file inventory, and MATLAB-Python interoperability. Includes static helper scripts that scan .m files, plan argv commands, and hash artifacts without executing anything. Use when writing or reviewing .m code, migrating code between MATLAB releases or to Octave, setting up reproducible tests and projects, inspecting an untrusted MAT or .mlx file safely, or checking Python Engine compatibility. Do not use for pure Python numerical work with NumPy or SciPy.
license: MIT
compatibility: Documentation is pinned where noted to proprietary MATLAB R2026a and free GNU Octave 11.3.0. Bundled Python CLIs require Python 3.11+ and run locally without MATLAB or Octave; optional MAT inventory uses scipy and/or h5py.
allowed-tools: Read Write Bash Glob Python
metadata:
  version: '1.2'
  category: data-science-and-ml
  maintainer: Kalaris Labs
  last-reviewed: '2026-07-23'
---

# MATLAB and GNU Octave

Use this skill to design or review numerical code, migrate MATLAB releases,
prepare reproducible projects, and plan trusted execution. MATLAB and GNU
Octave are distinct products: compatibility is partial, not a license or
behavior guarantee.

## Product and license gate

- **MATLAB R2026a is proprietary.** Do not assume MATLAB, MATLAB Online, a
  named toolbox, MATLAB Test, MATLAB Compiler, MATLAB Coder, Parallel Computing
  Toolbox, or an add-on is installed, licensed, or available to the user.
- **MATLAB Runtime is not MATLAB.** It runs compatible applications produced
  with MATLAB Compiler; it cannot run arbitrary source or host MATLAB Engine
  for Python. Building artifacts needs the applicable licensed compiler and
  every product used by the source.
- **GNU Octave 11.3.0 is free software under GPLv3+.** Octave packages are not
  MATLAB toolboxes. Similar names do not imply API, numerical, graphics, or
  licensing equivalence.
- Ask which runtime, release, platform, installed products, and license context
  the user actually has. Treat availability as `unknown` until confirmed.

See [Octave compatibility](references/octave-compatibility.md) and
[execution/product boundaries](references/executing-scripts.md).

## Nonnegotiable safety boundary

Never run an untrusted `.m`, `.mlx`, MEX binary, MAT file, project startup or
shutdown action, package installer, or generated artifact. Static review does
not prove safety.

Treat these as execution or code-loading surfaces:

- `eval`, `evalin`, `assignin`, text-derived `feval`, `str2func`, callbacks,
  timers, app callbacks, and dynamically modified paths;
- `system`, `unix`, `dos`, shell escape `!`, Java, .NET, Python (`py.*`,
  `pyrun`, `pyrunfile`), MEX, and native libraries;
- `mex`, `codegen`, MATLAB Compiler, build tasks, package/project startup, and
  generated code;
- `load`, object deserialization (`loadobj`, custom serialization), function
  handles, Java/System objects, and class code reachable from MAT files.

`.mlx` is an opaque archive for this toolkit and MEX is native executable code.
Do not use Python pickle for exchange. Inspect first, isolate when appropriate,
obtain explicit approval, then invoke a user-confirmed executable and license.
Bundled scripts are static or dry-run tools: none launches MATLAB, Octave,
Python Engine, a compiler, or a subprocess.

## Default workflow

1. **Clarify target.** Record MATLAB release or Octave version, OS/architecture,
   base product versus required toolboxes/packages, expected inputs/outputs,
   numerical tolerances, and whether execution is authorized.
2. **Inventory statically.** Scan `.m` files, opaque artifacts, project paths,
   required products, and MAT headers before any runtime loads them.
3. **Choose code form.** Prefer functions with an `arguments` block for
   automation. Use scripts only for controlled orchestration and live scripts
   for reviewed interactive narratives.
4. **Make semantics explicit.** Record shapes, classes, units, missing-value
   rules, indexing, implicit expansion, RNG algorithm/seed, tolerances, and
   output formats.
5. **Test without hidden state.** Keep fixtures synthetic, paths project-local,
   graphics deterministic, and tests independent of base-workspace residue.
6. **Plan execution.** Generate an argv plan, review startup/path effects and
   licenses, and launch only after explicit approval outside these helpers.
7. **Capture provenance.** Hash named inputs/code and record release, products,
   RNG policy, tolerances, and command plan without dumping the environment.

## Language and data checklist

### Scripts, functions, and live scripts

- Scripts share the caller/base workspace and leave variables behind.
  Functions have local workspaces and explicit inputs/outputs.
- Live scripts (`.mlx`) mix code and rich output but are not plain-text
  review artifacts. Export reviewed code to `.m` for static inspection.
- Avoid `clear all`, broad `addpath(genpath(...))`, dependence on `pwd`, global
  variables, and silent name shadowing. Use project roots and `fullfile`.
- Validate sizes, classes, and values in `arguments` blocks. Remember that
  type declarations can convert inputs; validators check without converting.
- A main function file should match the main function name. Local functions
  are private to the file; since R2024a they can appear anywhere in a script
  outside conditional contexts.

```matlab
function y = scaleSignal(x, options)
arguments
    x (:,1) double {mustBeFinite}
    options.Scale (1,1) double {mustBeFinite, mustBeNonzero} = 1
end
y = x .* options.Scale;
end
```

Read [programming](references/programming.md).

### Arrays, indexing, and numerics

- MATLAB uses 1-based, column-major indexing. `A(i,j)`, `A(k)`, `A(:,j)`,
  `A{...}`, and `A.(name)` have different semantics.
- `*`, `/`, `\`, and `^` are matrix operations; dotted forms are
  element-wise. Use `A\b`, not `inv(A)*b`.
- Since R2016b, compatible dimensions expand implicitly. Assert intended shape
  before operations that could accidentally form an outer result.
- Preallocate when output size is known, but do not vectorize at the cost of
  huge temporaries or unreadable code. Measure with `timeit` or the profiler.
- Compare floating-point results with domain-chosen absolute and relative
  tolerances, not blanket `==` or a magic multiple of `eps`.
- Pin both random algorithm and seed. Use named `RandStream` substreams for
  independent parallel work; do not use time-based `rng("shuffle")` for a
  reproducibility claim.

Read [arrays](references/matrices-arrays.md) and
[mathematics](references/mathematics.md).

### Tables, timetables, and missing values

- A `table` has named, equal-height variables that may have different types.
  `T(rows,vars)` returns a table; `T{rows,vars}` extracts contents; `T.Var`
  selects one variable.
- A `timetable` additionally has row times. Sort, validate time zones and
  uniqueness, then use `retime`/`synchronize` intentionally.
- Missing sentinels are type-specific: `NaN`, `NaT`, `<missing>`,
  `<undefined>`, and empty character vectors. Integer and logical arrays have
  no standard missing sentinel.
- Define import options rather than relying on inference for production data.
  Preserve units, time zones, variable names, encodings, and missing rules.

Read [data import/export](references/data-import-export.md).

## Graphics and export

Use explicit figure/axes handles and `tiledlayout`; label units; set limits,
color scales, font sizes, and colormaps deliberately. Prefer `exportgraphics`
over `saveas` for publication output. In R2026a it exports raster, PDF/EPS/EMF,
SVG, GIF, and interactive HTML; format capabilities differ. Specify
`ContentType="vector"` for suitable PDF/SVG-style output and `Resolution` for
raster output. Review accessibility and embedded-raster behavior.

Read [graphics and export](references/graphics-visualization.md).

## MAT files and exchange

- Version 7 is the normal `save` default; `matfile` creates 7.3 by default.
  Versions 4/6/7/7.3 differ in types, compression, and per-variable limits.
- Version 7.3 is HDF5-based, not an arbitrary HDF5 interchange contract.
  Partial access and chunking can help large arrays.
- Never load an untrusted MAT file. Inventory headers/datasets first. Objects
  can invoke class deserialization behavior; opaque/function/native content
  requires escalation.
- Prefer CSV/JSON/Parquet/HDF5 with a documented schema for simple exchange.
  Do not rename pickle payloads as MAT files and do not deserialize pickle.

Read [data import/export](references/data-import-export.md).

## Projects, analysis, and tests

- Use MATLAB Projects for controlled paths, startup/shutdown tasks,
  dependencies, source control, and reproducible entry points. Review project
  actions before opening an untrusted project.
- `matlab.codetools.requiredFilesAndProducts` and Dependency Analyzer are
  static approximations; dynamic dispatch can cause misses or false positives.
  A required-product report does not prove a license is available.
- Use Code Analyzer (`codeIssues`; legacy text workflows can use `checkcode`)
  and `codeCompatibilityReport` before migration.
- Base MATLAB includes script-, function-, and class-based
  `matlab.unittest` workflows. Parallel runs require Parallel Computing
  Toolbox. Dependency-based selection, richer quality dashboards, generated
  tests, and advanced coverage/equivalence features can require MATLAB Test or
  other products.
- R2026a `runtests` automatically opens and later closes a project when target
  tests belong to a project that is not already open. Account for startup and
  shutdown actions before using this behavior.

Read [programming](references/programming.md) and
[execution/testing](references/executing-scripts.md).

## Python integration, pinned to R2026a

- R2026a supports 64-bit CPython 3.9-3.13 for MATLAB Interface to Python,
  MATLAB Engine for Python, and MATLAB Compiler SDK for Python.
- The current R2026a PyPI package reviewed here is
  `matlabengine==26.1.12` (released 2026-05-08). It requires an installed
  R2026a; MATLAB Runtime alone is insufficient. R2026a also ships a
  preinstalled Engine distribution under one named `matlabroot` path.
- Package installation does not grant MATLAB or toolbox licenses. Configure
  one named interpreter/executable; do not print the full environment,
  `PATH`, `PYTHONPATH`, or credentials.
- `pyenv` controls MATLAB-to-Python interpreter selection. In-process Python
  generally requires restarting MATLAB to switch; out-of-process Python can
  be terminated and reconfigured.
- Starting Engine is an explicit execution action:
  `matlab.engine.start_matlab()` starts a MATLAB process and can check out a
  license. Never call it merely to probe availability.
- Verify conversion semantics for NumPy arrays, pandas DataFrames,
  tables/timetables, strings/missing values, datetime/duration, dictionaries,
  shape/order, and unsupported sparse/object/categorical cases.

Read [Python integration](references/python-integration.md).

## Local helper CLIs

Every helper is network-free, bounded, symlink-rejecting, and nonexecuting.
Run from this skill directory with Python 3.11+. Bash is allowed only to invoke
these Python CLIs and validation commands; never use it to execute a generated
MATLAB/Octave argv plan or untrusted artifact.

| Helper | Purpose |
|---|---|
| `scripts/plan_batch_command.py` | Produce reviewed MATLAB/Octave argv; never execute |
| `scripts/scan_m_code.py` | Scan `.m` text and flag opaque `.mlx`/MEX risks |
| `scripts/validate_project_manifest.py` | Validate paths and declared product/license status |
| `scripts/inventory_mat_file.py` | Header/metadata inventory; never call `loadmat` |
| `scripts/plan_python_compatibility.py` | Check R2026a CPython/Engine compatibility |
| `scripts/reproducibility_report.py` | Hash named local artifacts and emit a bounded report |
| `scripts/generate_function_scaffold.py` | Dry-run or create function and unit-test scaffolds |

```bash
python scripts/scan_m_code.py path/to/source --root path/to/project
python scripts/plan_batch_command.py matlab script path/to/main.m --root path/to/project
python scripts/validate_project_manifest.py project-manifest.json --root path/to/project
python scripts/inventory_mat_file.py data.mat --root path/to/project
python scripts/plan_python_compatibility.py --python-version 3.13
python scripts/reproducibility_report.py --root path/to/project --file src/analyze.m
python scripts/generate_function_scaffold.py analyzeSignal --root path/to/project
```

The scaffold generator defaults to dry-run; writing requires `--write` and
refuses collisions. SciPy and h5py are optional inventory backends; if
authorized, add exact reviewed versions to the caller's project lockfile.
They are not required for `--help` or header-only inventory, and this skill
does not perform package installation.

## References

- [Programming, workspaces, projects, analysis, tests](references/programming.md)
- [Matrices, indexing, types, missingness, performance](references/matrices-arrays.md)
- [Numerical methods, tolerances, RNG, toolbox boundaries](references/mathematics.md)
- [Graphics and `exportgraphics`](references/graphics-visualization.md)
- [Import/export, tables/timetables, MAT semantics and safety](references/data-import-export.md)
- [MATLAB/Octave command-line execution and migration](references/executing-scripts.md)
- [MATLAB and Python interoperability](references/python-integration.md)
- [GNU Octave 11.3.0 compatibility differences](references/octave-compatibility.md)

Bundled JSON assets are the [project manifest](assets/project_manifest_template.json),
[reproducibility manifest](assets/reproducibility_manifest_template.json), and
[R2026a Python table](assets/python_compatibility_r2026a.json). There is no
`templates/` directory and no Markdown file is loaded from `assets/`;
local-link tests enforce this package contract.

## Primary sources (verified 2026-07-23)

- [MATLAB R2026a documentation](https://www.mathworks.com/help/matlab/)
- [MATLAB R2026a release notes](https://www.mathworks.com/help/matlab/release-notes.html)
- [R2026a system requirements](https://www.mathworks.com/support/requirements/matlab-system-requirements.html)
- [Python compatibility by release](https://www.mathworks.com/support/requirements/python-compatibility.html)
- [MATLAB Engine installation](https://www.mathworks.com/help/matlab/matlab_external/install-the-matlab-engine-for-python.html)
- [GNU Octave 11.3.0 release](https://octave.org/)
- [GNU Octave current manual](https://docs.octave.org/latest/)