seqeval / README.md
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---
title: seqeval
emoji: 🤗
colorFrom: blue
colorTo: red
sdk: gradio
sdk_version: 3.19.1
app_file: app.py
pinned: false
tags:
- evaluate
- metric
description: >-
seqeval is a Python framework for sequence labeling evaluation.
seqeval can evaluate the performance of chunking tasks such as named-entity recognition, part-of-speech tagging, semantic role labeling and so on.
This is well-tested by using the Perl script conlleval, which can be used for
measuring the performance of a system that has processed the CoNLL-2000 shared task data.
seqeval supports following formats:
IOB1
IOB2
IOE1
IOE2
IOBES
See the [README.md] file at https://github.com/chakki-works/seqeval for more information.
---
# Metric Card for seqeval
## Metric description
seqeval is a Python framework for sequence labeling evaluation. seqeval can evaluate the performance of chunking tasks such as named-entity recognition, part-of-speech tagging, semantic role labeling and so on.
## How to use
Seqeval produces labelling scores along with its sufficient statistics from a source against one or more references.
It takes two mandatory arguments:
`predictions`: a list of lists of predicted labels, i.e. estimated targets as returned by a tagger.
`references`: a list of lists of reference labels, i.e. the ground truth/target values.
It can also take several optional arguments:
`suffix` (boolean): `True` if the IOB tag is a suffix (after type) instead of a prefix (before type), `False` otherwise. The default value is `False`, i.e. the IOB tag is a prefix (before type).
`scheme`: the target tagging scheme, which can be one of [`IOB1`, `IOB2`, `IOE1`, `IOE2`, `IOBES`, `BILOU`]. The default value is `None`.
`mode`: whether to count correct entity labels with incorrect I/B tags as true positives or not. If you want to only count exact matches, pass `mode="strict"` and a specific `scheme` value. The default is `None`.
`sample_weight`: An array-like of shape (n_samples,) that provides weights for individual samples. The default is `None`.
`zero_division`: Which value to substitute as a metric value when encountering zero division. Should be one of [`0`,`1`,`"warn"`]. `"warn"` acts as `0`, but the warning is raised.
```python
>>> seqeval = evaluate.load('seqeval')
>>> predictions = [['O', 'O', 'B-MISC', 'I-MISC', 'I-MISC', 'I-MISC', 'O'], ['B-PER', 'I-PER', 'O']]
>>> references = [['O', 'O', 'O', 'B-MISC', 'I-MISC', 'I-MISC', 'O'], ['B-PER', 'I-PER', 'O']]
>>> results = seqeval.compute(predictions=predictions, references=references)
```
## Output values
This metric returns a dictionary with a summary of scores for overall and per type:
Overall:
`accuracy`: the average [accuracy](https://huggingface.co/metrics/accuracy), on a scale between 0.0 and 1.0.
`precision`: the average [precision](https://huggingface.co/metrics/precision), on a scale between 0.0 and 1.0.
`recall`: the average [recall](https://huggingface.co/metrics/recall), on a scale between 0.0 and 1.0.
`f1`: the average [F1 score](https://huggingface.co/metrics/f1), which is the harmonic mean of the precision and recall. It also has a scale of 0.0 to 1.0.
Per type (e.g. `MISC`, `PER`, `LOC`,...):
`precision`: the average [precision](https://huggingface.co/metrics/precision), on a scale between 0.0 and 1.0.
`recall`: the average [recall](https://huggingface.co/metrics/recall), on a scale between 0.0 and 1.0.
`f1`: the average [F1 score](https://huggingface.co/metrics/f1), on a scale between 0.0 and 1.0.
### Values from popular papers
The 1995 "Text Chunking using Transformation-Based Learning" [paper](https://aclanthology.org/W95-0107) reported a baseline recall of 81.9% and a precision of 78.2% using non Deep Learning-based methods.
More recently, seqeval continues being used for reporting performance on tasks such as [named entity detection](https://www.mdpi.com/2306-5729/6/8/84/htm) and [information extraction](https://ieeexplore.ieee.org/abstract/document/9697942/).
## Examples
Maximal values (full match) :
```python
>>> seqeval = evaluate.load('seqeval')
>>> predictions = [['O', 'O', 'B-MISC', 'I-MISC', 'I-MISC', 'I-MISC', 'O'], ['B-PER', 'I-PER', 'O']]
>>> references = [['O', 'O', 'B-MISC', 'I-MISC', 'I-MISC', 'I-MISC', 'O'], ['B-PER', 'I-PER', 'O']]
>>> results = seqeval.compute(predictions=predictions, references=references)
>>> print(results)
{'MISC': {'precision': 1.0, 'recall': 1.0, 'f1': 1.0, 'number': 1}, 'PER': {'precision': 1.0, 'recall': 1.0, 'f1': 1.0, 'number': 1}, 'overall_precision': 1.0, 'overall_recall': 1.0, 'overall_f1': 1.0, 'overall_accuracy': 1.0}
```
Minimal values (no match):
```python
>>> seqeval = evaluate.load('seqeval')
>>> predictions = [['O', 'B-MISC', 'I-MISC'], ['B-PER', 'I-PER', 'O']]
>>> references = [['B-MISC', 'O', 'O'], ['I-PER', '0', 'I-PER']]
>>> results = seqeval.compute(predictions=predictions, references=references)
>>> print(results)
{'MISC': {'precision': 0.0, 'recall': 0.0, 'f1': 0.0, 'number': 1}, 'PER': {'precision': 0.0, 'recall': 0.0, 'f1': 0.0, 'number': 2}, '_': {'precision': 0.0, 'recall': 0.0, 'f1': 0.0, 'number': 1}, 'overall_precision': 0.0, 'overall_recall': 0.0, 'overall_f1': 0.0, 'overall_accuracy': 0.0}
```
Partial match:
```python
>>> seqeval = evaluate.load('seqeval')
>>> predictions = [['O', 'O', 'B-MISC', 'I-MISC', 'I-MISC', 'I-MISC', 'O'], ['B-PER', 'I-PER', 'O']]
>>> references = [['O', 'O', 'O', 'B-MISC', 'I-MISC', 'I-MISC', 'O'], ['B-PER', 'I-PER', 'O']]
>>> results = seqeval.compute(predictions=predictions, references=references)
>>> print(results)
{'MISC': {'precision': 0.0, 'recall': 0.0, 'f1': 0.0, 'number': 1}, 'PER': {'precision': 1.0, 'recall': 1.0, 'f1': 1.0, 'number': 1}, 'overall_precision': 0.5, 'overall_recall': 0.5, 'overall_f1': 0.5, 'overall_accuracy': 0.8}
```
## Limitations and bias
seqeval supports following IOB formats (short for inside, outside, beginning) : `IOB1`, `IOB2`, `IOE1`, `IOE2`, `IOBES`, `IOBES` (only in strict mode) and `BILOU` (only in strict mode).
For more information about IOB formats, refer to the [Wikipedia page](https://en.wikipedia.org/wiki/Inside%E2%80%93outside%E2%80%93beginning_(tagging)) and the description of the [CoNLL-2000 shared task](https://aclanthology.org/W02-2024).
## Citation
```bibtex
@inproceedings{ramshaw-marcus-1995-text,
title = "Text Chunking using Transformation-Based Learning",
author = "Ramshaw, Lance and
Marcus, Mitch",
booktitle = "Third Workshop on Very Large Corpora",
year = "1995",
url = "https://www.aclweb.org/anthology/W95-0107",
}
```
```bibtex
@misc{seqeval,
title={{seqeval}: A Python framework for sequence labeling evaluation},
url={https://github.com/chakki-works/seqeval},
note={Software available from https://github.com/chakki-works/seqeval},
author={Hiroki Nakayama},
year={2018},
}
```
## Further References
- [README for seqeval at GitHub](https://github.com/chakki-works/seqeval)
- [CoNLL-2000 shared task](https://www.clips.uantwerpen.be/conll2002/ner/bin/conlleval.txt)