提交 a74060d4 编写于 作者: Y yangyaming

modify usage document of chunk evaluator

上级 8411a73e
......@@ -347,32 +347,45 @@ def chunk_evaluator(
excluded_chunk_types=None, ):
"""
Chunk evaluator is used to evaluate segment labelling accuracy for a
sequence. It calculates the chunk detection F1 score.
sequence. It calculates precision, recall and F1 score of the chunk detection.
A chunk is correctly detected if its beginning, end and type are correct.
Other chunk type is ignored.
For each label in the label sequence, we have:
To use chunk evaluator, the construction of label dict should obey the following rules:
(1) Use one of the listed labelling schemes. These schemes differ in ways indicating chunk boundry.
.. code-block:: python
Scheme Begin Inside End Single
plain 0 - - -
IOB 0 1 - -
IOE - 0 1 -
IOBES 0 1 2 3
.. code-block:: python
To make it clear, let's illustrate by a NER example.
Assuming that there are two named entity types including ORG and PER which are called 'chunk type' here,
if 'IOB' scheme were used, the label set will be extended to a set including B-ORG, I-ORG, B-PER, I-PER and O,
in which B-ORG for begining of ORG and I-ORG for end of ORG.
Prefixes which are called 'tag type' here are added to chunk types and there are two tag types including B and I.
Of course, the training data should be labeled accordingly.
(2) Map can be done correctly by the listed equations.
.. code-block:: python
tagType = label % numTagType
chunkType = label / numTagType
otherChunkType = numChunkTypes
.. code-block:: python
The total number of different labels is numTagType*numChunkTypes+1.
We support 4 labelling scheme.
The tag type for each of the scheme is shown as follows:
Continue the NER example, and the label dict should like this to satify above equations:
.. code-block:: python
B-ORG 0
I-ORG 1
B-PER 2
I-PER 3
O 4
.. code-block:: python
Scheme Begin Inside End Single
plain 0 - - -
IOB 0 1 - -
IOE - 0 1 -
IOBES 0 1 2 3
'plain' means the whole chunk must contain exactly the same chunk label.
Realizing that the number of is chunk type is 2 and number of tag type is 2, it is easy to validate this.
The simple usage is:
......
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