| 
Rao et al. (2014)
 | 
Sentiment pruning strategies to improve word-level sentiment lexicons. | 
Sina Dataset, SemEval-2007 Dataset | 
1,854,718, 109,129 | 
| 
Han et al. (2018)
 | 
The unlabeled reviews are used to generate domain-specific sentiment lexicon | 
Movie Review Dataset, Amazon Dataset | 
50,000, 1,140,496 | 
| 
Liang, Liu & Zhang (2020)
 | 
After regularizing the dataset and using the Doc2vec+SVM method | 
Chinese Opinion Analysis Evaluation (COAE) 2013, COAE2015 | 
22,890, 30,049 | 
| 
Elgeldawi et al. (2021)
 | 
Five hyperparameter methods for hyperparameter tuning of machine learning algorithms | 
Hotel Review Dataset | 
7,000 | 
| 
Al-Hadhrami, Al-Fassam & Benhidour (2019)
 | 
Sentiment weights are calculated using TF-IDF and classified using machine learning. | 
Sentiment140 Dataset | 
1,578,612 | 
| 
Kim (2014)
 | 
CNN for extracting word character features | 
Movie Review (MR) Dataset, Stanford Sentiment Treebank (SST)-1 Dataset, SST-2 Dataset, Subjectivity Dataset, TREC Question Dataset, Customer reviews Dataset, Multi-Perspective Question Answering (MPQA) Dataset | 
10,662, 11,855, 9,613, 10,000, 5,952, 3,773, 10,604 | 
| 
Zaremba, Sutskever & Vinyals (2014)
 | 
LSTM extracts semantic information | 
Penn Tree Bank (PTB) Dataset | 
900,000 | 
| 
Wang (2022)
 | 
Improved LSTM framework for tourism theme feature extraction | 
Rural Tourism Dataset | 
18,566 | 
| 
Li & Ning (2020)
 | 
CNN and LSTM hybrid models are used to derive both local and global features | 
THUCNews Dataset | 
740,000 | 
| 
Wang & He (2022)
 | 
BiGRU is used to extract global information, while the attention mechanism performs feature weighting to emphasize important features | 
Weibo Sentiment 100k Binary Dataset | 
119,988 | 
| 
Zeng, Yang & Zhou (2022)
 | 
The topics are classified by LDA, and the text features are extracted by BiLSTM-ATT | 
COVID-19 Review Dataset | 
30,525 |