Profile
I am a researcher of data analytics belonging to
Mathematical Sciences team at IBM Research - Tokyo.
My interest is applying advanced machine learning algorithms
for i) fitting human behavior models, and
ii) deriving practical business insights such as marketing expertise.
Currently I study sparse nonparametric methods for density estimation and non-linear perception and response models of humans. My principal motivation is to solve real-world problems, especially required in marketing investment and risk management. Examples of the issues are
- What kind of stochastic process is appropriate for modeling the real-world phenomena?
- What types of intrinsic processes exist in one consumer's purchase decision?
- How are the distributions in real data different from simple parametric (e.g. Gaussian) distributions?
- How the response of a consumer to marketing investment (e.g. advertisement & promotion) is skewed?
- What kind of non-linear functions are suitable for modeling such phenomena?
- How is a person's decision and risk evaluation different from the normative and rational behavior model?
- What perspectives are effective to capture the heterogeneity among consumers?
- How can firms act efficiently when given evidences of idiosyncratic behaviors of humans?
For marketing research with relationship to the risk assessments, I have a personal opinion in which not the firm's but the customer's risk-attitudes are worth considering in designing products and services. Readers who are interested in this issue, please move to this column.
Contact Information
IBM Research - Tokyo
1623-14 Shimotsuruma, Yamato-shi, Kanagawa-ken 242-8502 Japan
e-mail: 
Education
- M.S. in Information Science and Technology, 2004, University of Tokyo, Tokyo, Japan
- B.Eng. in Information and Communication Engineering, 2002, University of Tokyo, Tokyo, Japan
Publications
Award
- (With team members) winning in ICDM Data Mining Contest , 2007
Journal Papers
- R. Takahashi, "Sequential Minimal Optimization in Convex Clustering Repetitions", Statistical Analysis and Data Mining, vol. 5(1), pp. 70–89, 2012
Conference Papers, Refereed
- R. Takahashi, T. Osogami, and T. Morimura "Large-Scale Nonparametric Estimation of Vehicle Travel Time Distributions", In proceedings of the 12th SIAM International Conference on Data Mining (SDM 2012), (to be appeared in Apr. 2012), 2012
- R. Takahashi, "Sequential Minimal Optimization in Adaptive-Bandwidth Convex Clustering", In proceedings of the 11th SIAM International Conference on Data Mining (SDM 2011), pp. 896-907, 2011 paper pdf(2.07MB) poster pdf(1,653KB)
- R. Takahashi, "Separating Precision and Mean in Dirichlet-Enhanced High-Order Markov Models", In proceedings of the 18th European Conference on Machine Learning (ECML 2007), pp. 382-393, 2007 paper pdf(194KB)
Other Papers
- Rikiya Takahashi and Takayuki Osogami, "Action-Sensitive Hidden Markov Model of Customer Behavior", In proceedings of New Directions of Research in Marketing (University of Tsukuba and Tohoku University), pp.119-134, 2006
- Rikiya Takahashi, Nobuaki Minematsu, and Keikichi Hirose, "Enhancing accuracy of dynamically interpolating language model using multiple backing-off N-grams", In proceedings of Special Interest Group of Spoken Language Processing (Information Processing Society of Japan), 49(11), pp.61-66, 2003
- Rikiya Takahashi, Nobuaki Minematsu, and Keikichi Hirose, "A dynamically context-adapted language model using multiple N-grams interpolation", In proceedings of Special Interest Group of Spoken Language Processing (Information Processing Society of Japan), 46(7)，pp.37-42, 2003
Personal Activities
Privately I am an amateur composer of orchestral music for film scoring. I have been impressed by late romantic scores including Arnold Schönberg, Gustav Mahler and Jean Sibelius. Moreover, I have adored the composers who are famous for film scores. Miklós Rózsa and Jerry Goldsmith have always been the centers in my emotional experiences. I can recommend "Ben-Hur", "El Cid", "Spellbound", "Papillon", "QB VII", "Firstblood", and "Rudy" for many listeners.
Examples of My Scores
- Rikiya Takahashi, "Prelude to Exodus", 2012 pdf(118KB)
- Rikiya Takahashi, "Passacaglia for String Quintent Op.1", 2008 pdf(540KB)
In vacations, I prefer to visit counties that have clystalline environments, such as North Europe. All of these crystal-clear lakes and mountains refresh my minds and give the energy for producing the next ideas in research and composition.
Hallstatt in Austria
Gullfoss in Iceland
Jökulsárlón
in Iceland