A Baseline for Multilingual Sentiment Analysis
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A Baseline for Multilingual Sentiment Analysis (B4MSA)

B4MSA is a Python Sentiment Analysis Classifier for Twitter-like short texts. It can be used to create a first approximation to a sentiment classifier on any given language. It is almost language-independent, but it can take advantage of the particularities of a language.

It is written in Python making use of NTLK, scikit-learn and gensim to create simple but effective sentiment classifiers.

Citing B4MSA

If you find B4MSA useful for any academic/scientific purpose, we would appreciate citations to the following journal paper:

A Simple Approach to Multilingual Polarity Classification in Twitter Eric S. Tellez, Sabino Miranda-Jiménez, Mario Graff, Daniela Moctezuma, Ranyart R. Suárez, Oscar S. Siordia. Pattern Recognition Letters.

@article{b4msa,
	title = {A {Simple} {Approach} to {Multilingual} {Polarity} {Classification} in {Twitter}},
	issn = {0167-8655},
	url = {http://www.sciencedirect.com/science/article/pii/S0167865517301721},
	doi = {10.1016/j.patrec.2017.05.024},
	abstract = {Recently, sentiment analysis has received a lot of attention due to the interest in mining opinions of social media users. Sentiment analysis consists in determining the polarity of a given text, i.e., its degree of positiveness or negativeness. Traditionally, Sentiment Analysis algorithms have been tailored to a specific language given the complexity of having a number of lexical variations and errors introduced by the people generating content. In this contribution, our aim is to provide a simple to implement and easy to use multilingual framework, that can serve as a baseline for sentiment analysis contests, and as a starting point to build new sentiment analysis systems. We compare our approach in eight different languages, three of them correspond to important international contests, namely, SemEval (English), TASS (Spanish), and SENTIPOLC (Italian). Within the competitions, our approach reaches from medium to high positions in the rankings; whereas in the remaining languages our approach outperforms the reported results.},
	urldate = {2017-05-24},
	journal = {Pattern Recognition Letters},
	author = {Tellez, Eric S. and Miranda-Jiménez, Sabino and Graff, Mario and Moctezuma, Daniela and Suárez, Ranyart R. and Siordia, Oscar S.},
	keywords = {Error-robust text representations, Multilingual sentiment analysis, Opinion mining},
	year = {2017}
}

A pre-print version can be found in arXiv:1612.05270

Performance

In order to know the performance of B4MSA, it was decided to compare B4MSA against different commercial sentiment analyzers such as: Google HP Haven, and Sentiment140. This comparison was performed on July 28, 2016.

The performance measures used in the comparison are taken from three different sentiment analysis competitions: TASS, SemEval, and SENTIPOLC. These measures are the accuracy, F1-positive-negative, and F0F1-positive-negative.

F1-positive-negative is defined as the average of the F1 obtained from the positive class and F1 of the negative class.

F0F1-positive-negative is defined as the average between F0-positive-negative and F1-positive-negative. F0-positive-negative is defined as the average of the F0 of the positive class and F0 of the negative class; F1-positive-negative is defined similarly. For more information regarding this measure we refer the reader to the overview of SENTIPOLC challenge

SENTIPOLC 2014 (Italian)

Algorithm Accuracy F1-positive-negative F0F1-positive-negative
HP Haven 0.4693 0.3921 0.4788
B4MSA 0.6072 0.6041 0.6354

TASS 2015-small (Spanish)

Algorithm Accuracy F1-positive-negative F0F1-positive-negative
HP Haven 0.5350 0.4564 0.5775
Sentiment140 0.0590 0.1001 0.3225
Meaning cloud 0.6500 0.6640 0.6471
B4MSA 0.6330 0.6949 0.6529

SemEval 2015 (English)

Algorithm Accuracy F1-positive-negative F0F1-positive-negative
HP Haven 0.6241 0.5724 0.6120
Google 0.4218 0.4967 0.4624
Sentiment140 0.5553 0.4790 0.5368
Meaning cloud 0.5775 0.5522 0.5361
B4MSA 0.6281 0.5281 0.6578

SemEval 2016 (English)

Algorithm Accuracy F1-positive-negative F0F1-positive-negative
HP Haven 0.5986 0.5173 0.5337
Google 0.3952 0.4728 0.4303
Sentiment140 0.5562 0.4135 0.4560
Meaning cloud 0.5252 0.5204 0.4861
B4MSA 0.5106 0.4082 0.4866

Note regarding Google:

Google's sentiment analysis algorithm does not provide classes instead the service returns a continuous value between -1 and 1; however, in the api documentation it was mentioned the following rule:

def get_class(pol):
    if pol < -0.75:
        return 'negative'
    elif pol > 0.25:
        return 'positive'
    return 'neutral'

Installing B4MSA

B4MSA can be installed using conda

conda install -c ingeotec b4msa

B4MSA can be installed using pip

pip install b4msa

or cloning the b4msa repository from github, e.g.,

git clone https://github.com/INGEOTEC/b4msa.git

Random search on the B4MSA's parameters space

Firstly, it is recommended to optimize the parameters used by B4MSA. In order to free the user from this task, B4MSA can perform a random search on the parameter space. B4MSA selects the best configuration found on the random search. Suppose you have a workload of classified tweets tweets.json.gz to model your problem, let us assume that b4msa is already installed. In order to optimize B4MSA parameters one can use the following command:

b4msa-params -k5 -s24 -n24 tweets.json.gz -o tweets.json

the parameters means for:

  • -k5 five folds
  • -s48 b4msa optimizes model's parameters for you, and -s48 specifies that the parameter space should be sampled in 48 points and it simply get the best among them
  • -n24 let us specify the number of workds to be launch, it is a good idea to set -s as a multiply of -n.
  • -o tweets.json specifies the file to store the configurations found by the parameter selection process, in best first order; a number of metrics are given, but it is in descending order by _score

The tweets.json looks like (for a four-classes problem)

[
  {
    "_accuracy": 0.7773561997268175,
    "_macro_f1": 0.5703751933361809,
    "_score": 0.5703751933361809,
    "_time": 36.73965764045715,
    "_weighted_f1": 0.7467834129359526,
    "del_dup1": false,
    "lc": true,
    "num_option": "group",
    "strip_diac": true,
    "token_list": [
      1,
      2,
      3,
      6
    ],
    "url_option": "none",
    "usr_option": "group"
  },
...

each entry specifies a configuration, please check the code (a manual is coming soon) to learn about each parameter. Since first configurations show how best/good setups are composed, it is possible to learn something about your dataset making some analysis on these setups.

There exist other useful flags like:

  • -H makes b4msa to perform last hill climbing search for the parameter selection, in many cases, this will produce much better configurations (never worst, guaranteed)
  • --lang spanish|english|italian it specifies the language of the dataset, it allows b4msa to use language dependent techniques to the parameter selection procedure; currently, only spanish is supported.
b4msa-params -H -k5 -s48 -n24 tweets.json.gz -o tweets-spanish.json --lang spanish

The tweets-spanish.json file looks as follows:

[
  {
    "_accuracy": 0.7750796782516315,
    "_macro_f1": 0.5736270120411987,
    "_score": 0.5736270120411987,
    "_time": 36.68731508255005,
    "_weighted_f1": 0.7472079134492694,
    "del_dup1": true,
    "lc": true,
    "negation": false,
    "num_option": "group",
    "stemming": true,
    "stopwords": "delete",
    "strip_diac": true,
    "token_list": [
      1,
      2,
      3,
      5
    ],
    "url_option": "delete",
    "usr_option": "none"
  },
...

Here we can see that negation, stemming and stopwords parameters were considered.

Training the model to create a sentiment classifier

At this point, we are in the position to train a model. Let us that the workload is tweets.json.gz and that the parameters are in tweets.json then the following command will save the model in b4msa.model

b4msa-train -o b4msa.model -m tweets.json tweets.json.gz

Testing a sentiment classifier against a workload

At this point, we are in the position to test the model (i.e, b4msa.model) in a new set. That is, we are in the position to ask the classifier to assign a polarity label to a particular text. For simplicity, let us assume that the new set is in tweets.json.gz and the predicted labels are stored in predicted.json.gz.

b4msa-test -m b4msa.model -o predicted.json.gz tweets.json.gz

Minimum requirements

In the modeling stage, the minimum requirements are dependent on the knowledge database being processed. Make sure you have enough memory for it. Take into account that b4msa can take advantage of multicore architectures using the multiprocessing module of python, this means that the memory requirements are multiplied by the number of processes you run.

It is recomended to use as many cores as you have to obtain good results in short running times.

On the training and testing stages only one core is used and there is no extra memory needs; however, no multicore support is provided for these stages.

Installing dependencies

Let us download python (from conda distribution), install it, and include python in the PATH.

wget http://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh
chmod 755 miniconda.sh
./miniconda.sh -b
export PATH=/home/$USER/miniconda3/bin:$PATH

B4MSA needs the following dependencies.

pip install coverage
pip install numpy
pip install scipy
pip install scikit-learn
pip install gensim
pip install nose
pip install nltk

For the eager people, it is recommended to install the tqdm package

pip install tqdm

However, it is better to prepare a coffee and a sandwich :)