How can I assess the impact of keyword positional?

223    Asked by DavidEdmunds in Data Science , Asked on Jul 15, 2024

 I am currently engaged in a particular task that is related to working on an NLP project where the task is to classify movie reviews as positive and negative. I have chosen to use a transformer-based model and I have executed keyword positional encoding to enhance the model’s focus on specific keywords such as “excellent”, “terrible” and “boring”. How should I assess the effectiveness of keyword positional encoding to improve the performance of the model? Describe the steps for me to take and the metrics should I choose for evaluating the impact of this particular approach. 

Answered by Cameron Oliver

In the context of data science, here are step-by-step explanations given:-

Baseline model training

You can train a baseline transformer-based model even without keyword positional encoding on the review of the movie dataset.

You can record the performance metrics such as precision and recall.

Implementation of keyword positional encoding

You can define a list of keywords such as “excellent”, “terrible” etc.You can modify the input embedding layer of the transformer to incorporate the keyword positional encoding.

Import torch
Import torch.nn as nn
Class KeywordPositionalEncoding(nn.Module):
    Def __init__(self, keywords, embedding_dim, max_len=512):
        Super(KeywordPositionalEncoding, self).__init__()
        Self.keywords = keywords
        Self.embedding_dim = embedding_dim
        Self.max_len = max_len
        Self.keyword_weights = {kw: I for I, kw in enumerate(keywords)}
    Def forward(self, tokens):
        Positions = torch.arange(0, self.max_len).unsqueeze(1).float()
        Position_encoding = positions / (10000 ** (2 * (positions // 2) / self.embedding_dim))
        # Encode keywords with additional positional information
        Keyword_positions = torch.zeros_like(tokens, dtype=torch.float)
        For idx, token in enumerate(tokens):
            If token in self.keyword_weights:
                Keyword_positions[idx] = self.keyword_weights[token]
        # Add keyword positional information to the standard positional encoding
        Return position_encoding + keyword_positions
# Usage in transformer
Embedding_dim = 768 # Assuming transformer embedding size is 768
Keyword_encoding = KeywordPositionalEncoding(keywords, embedding_dim)

Training of model with keyword positional encoding

You can train the modified transformer model by using the same dataset and also the training Configuration as the baseline model.

You can save the trained model for evaluation.

Evaluation and comparison

You can compare the performance of the model on the test set by using the same metrics as the baseline model.

You can use paired statistical tests such as paired tests to compare the performance of the model.

From scipy.stats import ttest_rel

  Baseline_scores = [0.85, 0.84, 0.86]  # Example scores for baseline model

Keyword_scores = [0.88, 0.87, 0.89] # Example scores for model with keyword encoding

# Conduct paired t-test
T_stat, p_value = ttest_rel(keyword_scores, baseline_scores) Print(f”T-statistic: {t_stat}, P-value: {p_value}”)Analyzing the attention Weights

You can visualize the attention Weights to see if the model with the keyword positional encoding is focusing more on the specific keywords.

You can also use the tools such as “bertviz” for attention visualization.

  From bertviz import head_view

# Assuming you have a function to get attention weights

Attention_weights = get_attention_weights(model_with_keyword_encoding, input_tokens)
Head_view(attention_weights, input_tokens)

Feature importance analysis

You can perform a feature importance analysis to understand the impact of keywords on the performance of the models.

You can use techniques such as SHAP (Shapely additives explanation) for this particular purpose.

Import shap

Explainer = shap.Explainer(model_with_keyword_encoding, data=X_test)
Shap_values = explainer(X_test)
Shap.summary_plot(shap_values, X_test)


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This step-by-step guide is extremely helpful. io games
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