davila7 / matchms

Skill Content

---
name: matchms
description: "Mass spectrometry analysis. Process mzML/MGF/MSP, spectral similarity (cosine, modified cosine), metadata harmonization, compound ID, for metabolomics and MS data processing."
---

# Matchms

## Overview

Matchms is an open-source Python library for mass spectrometry data processing and analysis. Import spectra from various formats, standardize metadata, filter peaks, calculate spectral similarities, and build reproducible analytical workflows.

## Core Capabilities

### 1. Importing and Exporting Mass Spectrometry Data

Load spectra from multiple file formats and export processed data:

```python
from matchms.importing import load_from_mgf, load_from_mzml, load_from_msp, load_from_json
from matchms.exporting import save_as_mgf, save_as_msp, save_as_json

# Import spectra
spectra = list(load_from_mgf("spectra.mgf"))
spectra = list(load_from_mzml("data.mzML"))
spectra = list(load_from_msp("library.msp"))

# Export processed spectra
save_as_mgf(spectra, "output.mgf")
save_as_json(spectra, "output.json")
```

**Supported formats:**
- mzML and mzXML (raw mass spectrometry formats)
- MGF (Mascot Generic Format)
- MSP (spectral library format)
- JSON (GNPS-compatible)
- metabolomics-USI references
- Pickle (Python serialization)

For detailed importing/exporting documentation, consult `references/importing_exporting.md`.

### 2. Spectrum Filtering and Processing

Apply comprehensive filters to standardize metadata and refine peak data:

```python
from matchms.filtering import default_filters, normalize_intensities
from matchms.filtering import select_by_relative_intensity, require_minimum_number_of_peaks

# Apply default metadata harmonization filters
spectrum = default_filters(spectrum)

# Normalize peak intensities
spectrum = normalize_intensities(spectrum)

# Filter peaks by relative intensity
spectrum = select_by_relative_intensity(spectrum, intensity_from=0.01, intensity_to=1.0)

# Require minimum peaks
spectrum = require_minimum_number_of_peaks(spectrum, n_required=5)
```

**Filter categories:**
- **Metadata processing**: Harmonize compound names, derive chemical structures, standardize adducts, correct charges
- **Peak filtering**: Normalize intensities, select by m/z or intensity, remove precursor peaks
- **Quality control**: Require minimum peaks, validate precursor m/z, ensure metadata completeness
- **Chemical annotation**: Add fingerprints, derive InChI/SMILES, repair structural mismatches

Matchms provides 40+ filters. For the complete filter reference, consult `references/filtering.md`.

### 3. Calculating Spectral Similarities

Compare spectra using various similarity metrics:

```python
from matchms import calculate_scores
from matchms.similarity import CosineGreedy, ModifiedCosine, CosineHungarian

# Calculate cosine similarity (fast, greedy algorithm)
scores = calculate_scores(references=library_spectra,
                         queries=query_spectra,
                         similarity_function=CosineGreedy())

# Calculate modified cosine (accounts for precursor m/z differences)
scores = calculate_scores(references=library_spectra,
                         queries=query_spectra,
                         similarity_function=ModifiedCosine(tolerance=0.1))

# Get best matches
best_matches = scores.scores_by_query(query_spectra[0], sort=True)[:10]
```

**Available similarity functions:**
- **CosineGreedy/CosineHungarian**: Peak-based cosine similarity with different matching algorithms
- **ModifiedCosine**: Cosine similarity accounting for precursor mass differences
- **NeutralLossesCosine**: Similarity based on neutral loss patterns
- **FingerprintSimilarity**: Molecular structure similarity using fingerprints
- **MetadataMatch**: Compare user-defined metadata fields
- **PrecursorMzMatch/ParentMassMatch**: Simple mass-based filtering

For detailed similarity function documentation, consult `references/similarity.md`.

### 4. Building Processing Pipelines

Create reproducible, multi-step analysis workflows:

```python
from matchms import SpectrumProcessor
from matchms.filtering import default_filters, normalize_intensities
from matchms.filtering import select_by_relative_intensity, remove_peaks_around_precursor_mz

# Define a processing pipeline
processor = SpectrumProcessor([
    default_filters,
    normalize_intensities,
    lambda s: select_by_relative_intensity(s, intensity_from=0.01),
    lambda s: remove_peaks_around_precursor_mz(s, mz_tolerance=17)
])

# Apply to all spectra
processed_spectra = [processor(s) for s in spectra]
```

### 5. Working with Spectrum Objects

The core `Spectrum` class contains mass spectral data:

```python
from matchms import Spectrum
import numpy as np

# Create a spectrum
mz = np.array([100.0, 150.0, 200.0, 250.0])
intensities = np.array([0.1, 0.5, 0.9, 0.3])
metadata = {"precursor_mz": 250.5, "ionmode": "positive"}

spectrum = Spectrum(mz=mz, intensities=intensities, metadata=metadata)

# Access spectrum properties
print(spectrum.peaks.mz)           # m/z values
print(spectrum.peaks.intensities)  # Intensity values
print(spectrum.get("precursor_mz")) # Metadata field

# Visualize spectra
spectrum.plot()
spectrum.plot_against(reference_spectrum)
```

### 6. Metadata Management

Standardize and harmonize spectrum metadata:

```python
# Metadata is automatically harmonized
spectrum.set("Precursor_mz", 250.5)  # Gets harmonized to lowercase key
print(spectrum.get("precursor_mz"))   # Returns 250.5

# Derive chemical information
from matchms.filtering import derive_inchi_from_smiles, derive_inchikey_from_inchi
from matchms.filtering import add_fingerprint

spectrum = derive_inchi_from_smiles(spectrum)
spectrum = derive_inchikey_from_inchi(spectrum)
spectrum = add_fingerprint(spectrum, fingerprint_type="morgan", nbits=2048)
```

## Common Workflows

For typical mass spectrometry analysis workflows, including:
- Loading and preprocessing spectral libraries
- Matching unknown spectra against reference libraries
- Quality filtering and data cleaning
- Large-scale similarity comparisons
- Network-based spectral clustering

Consult `references/workflows.md` for detailed examples.

## Installation

```bash
uv pip install matchms
```

For molecular structure processing (SMILES, InChI):
```bash
uv pip install matchms[chemistry]
```

## Reference Documentation

Detailed reference documentation is available in the `references/` directory:
- `filtering.md` - Complete filter function reference with descriptions
- `similarity.md` - All similarity metrics and when to use them
- `importing_exporting.md` - File format details and I/O operations
- `workflows.md` - Common analysis patterns and examples

Load these references as needed for detailed information about specific matchms capabilities.