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thai2vec

State-of-the-Art Language Modeling, Text Feature Extraction and Text Classification in Thai Language. Created as part of pyThaiNLP with ULMFit implementation from fast.ai

Models and word embeddings can also be downloaded via Google Drive or Dropbox.

We provide state-of-the-art language modeling (perplexity of 34.87803 on Thai wikipedia) and text classification (micro-averaged F-1 score of 0.60925 on 5-label classification problem. Benchmarked to 0.49366 by fastText on Wongnai Challenge: Review Rating Prediction. The language model can also be used to extract text features for other downstream tasks.

random word vectors

Dependencies

  • Python 3.6.5
  • PyTorch 0.4.0
  • fast.ai

Version History

v0.1

  • Pretrained language model based on Thai Wikipedia with the perplexity of 46.61
  • Pretrained word embeddings (.vec) with 51,556 tokens and 300 dimensions
  • Classification benchmark of 94.4% accuracy compared to 65.2% by fastText for 4-label classification of BEST

v0.2

  • Refactored to use fastai.text instead of torchtext
  • Pretrained language model based on Thai Wikipedia with the perplexity of 34.87803 (pretrain_wiki.ipynb)
  • Pretrained word embeddings (.vec and .bin) with 60,000 tokens and 300 dimensions (word2vec_examples.ipynb)
  • Classification benchmark of 0.60925 micro-averaged F1 score compared to 0.49366 by fastText and 0.58139 by competition winner for 5-label classification of Wongnai Challenge: Review Rating Prediction (ulmfit_wongnai.ipynb)
  • Text feature extraction for other downstream tasks such as clustering (ulmfit_ec.ipynb)

Word Embeddings

The thai2vec.vec contains 60,000 word embeddings (plus padding and unknown tokens) of 300 dimensions, in descending order by their frequencies (See thai2vec.vocab). The files are in word2vec format readable by gensim. Most common applications include word vector visualization, word arithmetic, word grouping, cosine similarity and sentence or document vectors. For sample code, see word2vec_examples.ipynb.

Word Arithmetic

You can do simple "arithmetic" with words based on the word vectors such as:

  • ผู้หญิง (female) + ราชา (king) - ผู้ชาย (male) = ราชินี (queen)
  • หุ้น (stock) - พนัน (gambling) = กิจการ (business)
  • อเมริกัน (american) + ฟุตบอล (football) = เบสบอล (baseball)

word arithmetic

Word Grouping

It can also be used to do word groupings. For instance:

  • อาหารเช้า อาหารสัตว์ อาหารเย็น อาหารกลางวัน (breakfast animal-food dinner lunch) - อาหารสัตว์ (animal-food) is type of food whereas others are meals in the day
  • ลูกสาว ลูกสะใภ้ ลูกเขย ป้า (duaghter daughter-in-law son-in-law aunt) - ลูกสาว (daughter) is immediate family whereas others are not
  • กด กัด กิน เคี้ยว (press bite eat chew) - กด (press) is not verbs for the eating process Note that this could be relying on a different "take" than you would expect. For example, you could have answered ลูกเขย in the second example because it is the one associated with male gender.

word grouping

Cosine Similarity

Calculate cosine similarity between two word vectors.

  • จีน (China) and ปักกิ่ง (Beijing): 0.31359560752667964
  • อิตาลี (Italy) and โรม (Rome): 0.42819627065839394
  • ปักกิ่ง (Beijing) and โรม (Rome): 0.27347283956785434
  • จีน (China) and โรม (Rome): 0.02666692964073511
  • อิตาลี (Italy) and ปักกิ่ง (Beijing): 0.17900795797557473

cosine similarity

Language Modeling

Thai word embeddings and language model are trained using the fast.ai version of AWD LSTM Language Model--basically LSTM with droupouts--with data from Wikipedia (last updated May 21, 2018). Using 80/20 train-validation split, we achieved perplexity of 34.87803 with 60,002 embeddings at 300 dimensions, compared to state-of-the-art as of June 12, 2018 at 40.68 for English WikiText-2 by Yang et al (2017) and 29.2 for English WikiText-103 by Rae et al (2018). To the best of our knowledge, there is no comparable research in Thai language at the point of writing (June 12, 2018). See pretrain_wiki.ipynb for more details.

Text Classification

We trained the ULMFit model implemented bythai2vec for text classification. We use Wongnai Challenge: Review Rating Prediction as our benchmark as it is the only sizeable and publicly available text classification dataset at the time of writing (June 21, 2018). It has 39,999 reviews for training and validation, and 6,203 reviews for testing.

We achieved validation perplexity at 35.75113 and validation micro F1 score at 0.598 for five-label classification. Micro F1 scores for public and private leaderboards are 0.61451 and 0.60925 respectively (supposedly we could train further with the 15% validation set we did not use), which are state-of-the-art as of the time of writing (June 21, 2018). FastText benchmark based on their own pretrained embeddings has the performance of 0.50483 and 0.49366 for public and private leaderboards respectively. See ulmfit_wongnai.ipynb for more details.

Text Feature Extraction

The pretrained language model of thai2vec can be used to convert Thai texts into vectors (roll credits!), after which said vectors can be used for various machine learning tasks such as classification, clustering, translation, question answering and so on. The idea is to train a language model that "understands" the texts then extract certain vectors that the model "thinks" represents the texts we want. We use 113,962 product reviews scraped from an ecommerce website as our sample dataset. See ulmfit_ec.ipynb for more details.