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Hajime Seya

Publications and source records attributed to Hajime Seya.

8 recordsLinked to original sources
arXiv2026

Scalable coarse-to-fine spatial downscaling

This study proposes coarse-to-fine downscaling (CF-DS), a scalable spatial downscaling method extending coarse-to-fine spatial modeling. Unlike conventional spatial-statistical downscaling methods such as area-to-point kriging, CF-DS does not require covariance matrix inversion or likelihood evaluation. Instead, it represents latent spatial processes through the synthesis of multi-scale local models, substantially reducing computational cost while approximately satisfying the aggregation constraint. Monte Carlo experiments show that CF-DS achieves predictive accuracy comparable to area-to-point kriging with dramatically shorter computation times, particularly for large datasets. An application to downscaling electricity consumption in the Tokyo metropolitan area further demonstrates its practical usefulness. The results suggest that CF-DS provides an efficient alternative for large-scale spatial downscaling problems. CF-DS is implemented in an R package spCF (https://cran.r-project.org/web/packages/spCF/index.html).

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arXiv2024

Sub-model aggregation for scalable eigenvector spatial filtering: Application to spatially varying coefficient modeling

This study proposes a method for aggregating/synthesizing global and local sub-models for fast and flexible spatial regression modeling. Eigenvector spatial filtering (ESF) was used to model spatially varying coefficients and spatial dependence in the residuals by sub-model, while the generalized product-of-experts method was used to aggregate these sub-models. The major advantages of the proposed method are as follows: (i) it is highly scalable for large samples in terms of accuracy and computational efficiency; (ii) it is easily implemented by estimating sub-models independently first and aggregating/averaging them thereafter; and (iii) likelihood-based inference is available because the marginal likelihood is available in closed-form. The accuracy and computational efficiency of the proposed method are confirmed using Monte Carlo simulation experiments. This method was then applied to residential land price analysis in Japan. The results demonstrate the usefulness of this method for improving the interpretability of spatially varying coefficients. The proposed method is implemented in an R package spmoran (version 0.3.0 or later).

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arXiv2021

Spatial prediction of apartment rent using regression-based and machine learning-based approaches with a large dataset

Employing a large dataset (at most, the order of n = 10^6), this study attempts enhance the literature on the comparison between regression and machine learning (ML)-based rent price prediction models by adding new empirical evidence and considering the spatial dependence of the observations. The regression-based approach incorporates the nearest neighbor Gaussian processes (NNGP) model, enabling the application of kriging to large datasets. In contrast, the ML-based approach utilizes typical models: extreme gradient boosting (XGBoost), random forest (RF), and deep neural network (DNN). The out-of-sample prediction accuracy of these models was compared using Japanese apartment rent data, with a varying order of sample sizes (i.e., n = 10^4, 10^5, 10^6). The results showed that, as the sample size increased, XGBoost and RF outperformed NNGP with higher out-of-sample prediction accuracy. XGBoost achieved the highest prediction accuracy for all sample sizes and error measures in both logarithmic and real scales and for all price bands (when n = 10^5 and 10^6). A comparison of several methods to account for the spatial dependence in RF showed that simply adding spatial coordinates to the explanatory variables may be sufficient.

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arXiv2019

A comparison of apartment rent price prediction using a large dataset: Kriging versus DNN

The hedonic approach based on a regression model has been widely adopted for the prediction of real estate property price and rent. In particular, a spatial regression technique called Kriging, a method of interpolation that was advanced in the field of spatial statistics, are known to enable high accuracy prediction in light of the spatial dependence of real estate property data. Meanwhile, there has been a rapid increase in machine learning-based prediction using a large (big) dataset and its effectiveness has been demonstrated in previous studies. However, no studies have ever shown the extent to which predictive accuracy differs for Kriging and machine learning techniques using big data. Thus, this study compares the predictive accuracy of apartment rent price in Japan between the nearest neighbor Gaussian processes (NNGP) model, which enables application of Kriging to big data, and the deep neural network (DNN), a representative machine learning technique, with a particular focus on the data sample size (n = 10^4, 10^5, 10^6) and differences in predictive performance. Our analysis showed that, with an increase in sample size, the out-of-sample predictive accuracy of DNN approached that of NNGP and they were nearly equal on the order of n = 10^6. Furthermore, it is suggested that, for both higher and lower end properties whose rent price deviates from the median, DNN may have a higher predictive accuracy than that of NNGP.

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arXiv2018

Spatially filtered unconditional quantile regression: Application to a hedonic analysis

Unconditional quantile regression (UQR) attracts attention in various fields to investigate the impacts of explanatory variables on quantiles of the marginal distribution of an explained variable. This study attempts to introduce spatial dependence into the UQR within the framework of random effects eigenvector spatial filtering, resulting in the model that we term the spatially filtered UQR (SF-UQR). We then develop a computationally efficient approach for SF-UQR estimation. Finally, the performance of the SF-UQR is tested with a hedonic land price model for the Tokyo metropolitan area. SF-UQR is implemented in an R package, "spmoran."

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arXiv2018

Low rank spatial econometric models

This article presents a re-structuring of spatial econometric models in a linear mixed model framework. To that end, it proposes low rank spatial econometric models that are robust to the existence of noise (i.e., measurement error), and can enjoy fast parameter estimation and inference by Type II restricted likelihood maximization (empirical Bayes) techniques. The small sample properties of the proposed low rank spatial econometric models are examined using Monte Carlo simulation experiments, the results of these experiments confirm that direct effects and indirect effects a la LeSage and Pace (2009) can be estimated with a high degree of accuracy. Also, when data are noisy, estimators for coefficients in the proposed models have lower root mean squared errors compared to conventional specifications, despite them being low rank approximations. The proposed approach is implemented in an R package "spmoran".

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arXiv2016

A Moran coefficient-based mixed effects approach to investigate spatially varying relationships

This study develops a spatially varying coefficient model by extending the random effects eigenvector spatial filtering model. The developed model has the following properties: its coefficients are interpretable in terms of the Moran coefficient; each of its coefficients can have a different degree of spatial smoothness; and it yields a variant of a Bayesian spatially varying coefficient model. Also, parameter estimation of the model can be executed with a relatively small computationally burden. Results of a Monte Carlo simulation reveal that our model outperforms a conventional eigenvector spatial filtering (ESF) model and geographically weighted regression (GWR) models in terms of the accuracy of the coefficient estimates and computational time. We empirically apply our model to the hedonic land price analysis of flood risk in Japan.

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