基于深度神经网络融合的大蒜价格预测组合模型

    Hybrid model for garlic price prediction based on deep neural network fusion

    • 摘要: 针对目前大蒜价格数据波动性高、影响因素复杂以及传统单一预测模型精度低等问题,该研究提出以两阶段特征选择、子模型结构适配与融合深度学习网络非线性优化为核心的大蒜价格精准预测组合模型。首先,利用最大相关最小冗余法(maximum relevance and minimum redundancy algorithm,mRMR)和最小绝对收缩和选择算子回归(least absolute shrinkage and selection,LASSO)算法进行两阶段特征选择,选取与大蒜价格高度相关的关键变量进行辅助预测。针对不同尺度的特征,构建两种预测子模型,一方面,将所选择的影响因素及大蒜历史价格输入到双向长短期记忆(bidirectional long short-term memory,BiLSTM)网络得到预测序列。另一方面,采用变分模态分解(variational mode decomposition,VMD)对大蒜价格原始序列进行分解,分解后的多个本征模态函数(intrinsic mode functions,IMFs)分别输入到深度混合核极限学习机(deep hybrid kernel extreme learning machine,DHKELM)模型进行预测,将各模态的预测结果重构得到预测的价格序列。为进一步提升预测性能,采用黑翅鸢优化算法(black-winged kite algorithm,BKA)优化DHKELM模型,采用贝叶斯优化算法(bayesian optimization,BYS)优化BiLSTM模型。最后,将单一子模型的预测结果输入到基于注意力机制的卷积神经网络-双向门控循环单元(CNN-BiGRU-Attention)进行融合,构建深度神经网络融合的非线性组合模型,实现非线性组合预测。试验结果表明,所构建的组合模型的平均绝对百分比误差(mean absolute percentage error,MAPE)、均方根误差(root mean square error,RMSE)和决定系数(coefficient of 经网络融合的非线性组合模型,实现非线性组合预测。试验结果表明,所构建的组合模型的平均绝对百分比误差(mean absolute percentage error,MAPE)、均方根误差(root mean square error,RMSE)和决定系数(coefficient of determination,R2)分别为1.61%、0.078元/斤和0.976R2比其成员子模型均提高,且其预测性能明显优于其他线性组合模型,大蒜价格预测精度显著提升。研究结果为大蒜市场决策与调控管理提供了参考,同时为其他农产品价格预测提供可复用的技术框架。

       

      Abstract: An accurate prediction of the garlic price can be one of the most important tasks in modern agriculture. However, the conventional single forecasting models are often limited to the high volatility of the garlic price data due to the complex and intertwined influencing factors. In this study, a high-precision ensemble prediction framework was proposed using deep learning fusion. Three modules were the two-stage feature selection, adaptive sub-model construction, and nonlinear optimization. Firstly, the two-stage feature selection was implemented to integrate the maximum relevance and minimum redundancy (mRMR) algorithm with the least absolute shrinkage and selection operator (LASSO) regression. The mRMR algorithm selected the features to maximize their correlation with the target variable. While the redundancy of the features was minimized to filter out the irrelevant and overlapping variables, in order to reduce the computational complexity and noise interference. The LASSO was used to further refine the subset. The L1 regularization was applied to promote the sparsity in the coefficients and the robustness to suppress the multicollinearity. The resulting feature subset contained the most informative variables that highly correlated with the garlic prices, providing a reliable input for the subsequent modeling. Secondly, two complementary sub-models were designed to solve the multi-scale variability in the garlic prices. The influencing factors and historical garlic prices were input into a bidirectional long short-term memory (BiLSTM) network. Temporal dependencies were captured in both forward and backward directions using BiLSTM. Nonlinear relationships were simulated for a stable prediction sequence. The original series of the garlic price was decomposed by variational mode decomposition (VMD) into several intrinsic mode functions (IMFs) with frequency components. Each IMF was modeled using a deep hybrid kernel extreme learning machine (DHKELM). The global and local kernel advantages were integrated to effectively learn the nonlinear patterns within each component. The prediction of the IMFs was reconstructed to form the final forecast sequence, thereby enhancing the interpretability of the low-frequency trends and high-frequency fluctuations. Thirdly, the advanced optimization was introduced to further enhance the model performance and convergence efficiency. The black-winged kite algorithm (BKA) was employed to optimize the kernel parameters and hidden-layer nodes of the DHKELM. The global search was improved to avoid the local optima. Meanwhile, Bayesian optimization (BYS) was used to fine-tune the BiLSTM hyperparameters, such as the learning rate, number of neurons, and batch size, indicating the high convergence and better generalization. Finally, the outputs of the sub-models were fused using a nonlinear ensemble structure with a convolutional neural network, bidirectional gated recurrent unit, and attention mechanism (CNN–BiGRU–Attention), instead of conventional linear averaging. The CNN was used to extract the local nonlinear interactions among the sub-model outputs. While the BiGRU was adopted to capture the long-term temporal dependencies and cross-period correlations. The attention layer dynamically assigned the adaptive weights to the important time steps and high-performing sub-models. Meanwhile, the end-to-end nonlinear prediction was fused to effectively reduce the accumulated errors for the complementary information. Experimental results demonstrate that the ensemble model achieved a mean absolute percentage error (MAPE) of 1.61%, a root mean square error (RMSE) of 0.078, and a coefficient of determination (R²) of 0.976. The R² value was improved by approximately 2%–7%, compared with the individual sub-models. The ensemble model also outperformed the conventional linear combination in terms of stability and accuracy. The forecasting precision of the garlic price was significantly enhanced after optimization. The framework can also provide a quantitative decision-making reference for the garlic market regulation. The finding can also serve as a reusable foundation for the price prediction of the agricultural commodities that are characterized by high volatility, complex interactions, and nonlinear dynamics.

       

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