<p>It is widely acknowledged that real-world data tend to complex and heterogeneous, often consisting of multimodal, unstructured, and noisy components. Estimating the posterior probability <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:P\left(\mathcal{C}=c|X=\mathbf{x}\right)\)</EquationSource> </InlineEquation> is a fundamental aspect of statistical classification. Unlike conventional approaches that model this global probability directly with a single complex function, we propose the more principled approach based on probabilistic decomposition. Specifically, we factorize the posterior probability <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\:P\left(\mathcal{C}|X=\mathbf{x}\right)\)</EquationSource> </InlineEquation> as <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\:P\left(\mathcal{C}=c|X=\mathbf{x}\right)={\sum\:}_{k}P\left({\Gamma\:}=k|X=\mathbf{x}\right)\cdot\:P\left(\mathcal{C}=c|{\Gamma\:}=k,\:X=\mathbf{x}\right)\)</EquationSource> </InlineEquation>, where <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\:{\Gamma\:}\)</EquationSource> </InlineEquation> denotes a latent variable that captures local structure or context. This decomposition enables modular learning and provides a flexible framework for modeling complex distributions. In this framework, the Fuzzy C-Means clustering algorithm models the gating probability <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\:P\left({\Gamma\:}=k|X=\mathbf{x}\right)\)</EquationSource> </InlineEquation>, representing the membership degree of the input data <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\:\mathbf{x}\)</EquationSource> </InlineEquation> to a fuzzy sub-region <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\:k\)</EquationSource> </InlineEquation>. To model the local posterior distribution <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\:P\left(\mathcal{C}=c|{\Gamma\:}=k,\:X=\mathbf{x}\right)\)</EquationSource> </InlineEquation>, we assign an independent Multi-Layer Perceptron (MLP) to each sub-region, where each MLP estimates the local class distribution through an output layer activated by softmax function. To evaluate the performance of the proposed model, we conduct extensive experiments using diverse machine learning datasets from the UCI Machine Learning Repository and a real-world dataset. The experimental results demonstrate that the proposed model consistently outperforms conventional global models in terms of the classification accuracy by effectively capturing the local characteristics of the data.</p>

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A Probabilistic Decomposition-Based Mixture of Experts Model with Fuzzy C-Means Gating

  • Seok-Beom Roh

摘要

It is widely acknowledged that real-world data tend to complex and heterogeneous, often consisting of multimodal, unstructured, and noisy components. Estimating the posterior probability \(\:P\left(\mathcal{C}=c|X=\mathbf{x}\right)\) is a fundamental aspect of statistical classification. Unlike conventional approaches that model this global probability directly with a single complex function, we propose the more principled approach based on probabilistic decomposition. Specifically, we factorize the posterior probability \(\:P\left(\mathcal{C}|X=\mathbf{x}\right)\) as \(\:P\left(\mathcal{C}=c|X=\mathbf{x}\right)={\sum\:}_{k}P\left({\Gamma\:}=k|X=\mathbf{x}\right)\cdot\:P\left(\mathcal{C}=c|{\Gamma\:}=k,\:X=\mathbf{x}\right)\) , where \(\:{\Gamma\:}\) denotes a latent variable that captures local structure or context. This decomposition enables modular learning and provides a flexible framework for modeling complex distributions. In this framework, the Fuzzy C-Means clustering algorithm models the gating probability \(\:P\left({\Gamma\:}=k|X=\mathbf{x}\right)\) , representing the membership degree of the input data \(\:\mathbf{x}\) to a fuzzy sub-region \(\:k\) . To model the local posterior distribution \(\:P\left(\mathcal{C}=c|{\Gamma\:}=k,\:X=\mathbf{x}\right)\) , we assign an independent Multi-Layer Perceptron (MLP) to each sub-region, where each MLP estimates the local class distribution through an output layer activated by softmax function. To evaluate the performance of the proposed model, we conduct extensive experiments using diverse machine learning datasets from the UCI Machine Learning Repository and a real-world dataset. The experimental results demonstrate that the proposed model consistently outperforms conventional global models in terms of the classification accuracy by effectively capturing the local characteristics of the data.