SparseM: A Sparse Matrix Package for R *

SparseM provides some basic R functionality for linear algebra with sparse matrices. Use of the package is illustrated by a family of linear model fitting functions that implement least squares methods for problems with sparse design matrices. Significant performance improvements in memory utilization and computational speed are possible for applications involving large sparse matrices.

The Adverse Impact of Temperature on Income

Crop Production/Industries, Risk and Uncertainty,

A fast and efficient implementation of qualitatively constrained quantile smoothing splines: Working paper series--05-08

Exploiting the sparse structure of the design matrices involved in the Frisch-Newton method, we implement a fast and efficient algorithm to compute qualitatively constrained smoothing and regression splines for quantile regression. In a previous implementation (He and Ng, 1999), the linear program involved was solved using the non-simplex active set algorithm for quantile smoothing spines proposed by Ng (1996). The current implementation uses the Frisch-Newton algorithm described in Koenker and Ng (2005a, 2005b). It is a variant of the interiorpoint algorithm proposed by Portnoy and Koenker (1997) which has been shown to outperform the simplex method in many applications. The current implementation relies on the R package SparseM of Koenker and Ng (2003) which contains a collection of basic linear algebra routines for sparse matrices to exploit the sparse structure of the matrices involved in the linear program to further speed up computation and save memory usage. A small simulation illustrates the superior performance of the new implementation

XLR: A free Excel add-in for introductory business statistics

XLR is an Excel add-in that unifies the user friendly, widely popular interface of Excel with the powerful and robust computational capability of the GNU statistical and graphical language R. The add-in attempts to address the American Statistical Association’s comment that “Generic packages such as Excel are not sufficient even for the teaching of sta- tistics, let alone for research and consulting.” R is the program of choice for researchers in statistical methodology that is freely available under the Free Software Foundation’s GNU General Public License (GPL) Agreement. By wedding the interactive mode of Excel with the power of statistical computing of R, XLR provides a solution to the problem of numerical inaccuracy of using Excel and its various internal statistical functions and procedures by harnessing the computational power of R. XLR will be distributed under the GNU GPL Agreement. The GPL puts students, instructors and researchers in control of their usage of the software by providing them with the freedom to run, copy, distribute, study, change and improve the software, thus, freeing them from the bondage of proprietary software. The creation of XLR will not only have a significant impact on the teaching of an Introductory Business Statistics course by providing a free alternative to the commercial proprietary software but also provide researchers in all disciplines who require so- phisticated and cutting edge statistical and graphical procedures with a user-friendly interactive data analysis tool when the current set of available commands is expanded to include more advance procedures

Vision-Based Three Dimensional Hand Interaction In Markerless Augmented Reality Environment

Kemunculan realiti tambahan membolehkan objek maya untuk wujud bersama dengan dunia sebenar dan ini memberi kaedah baru untuk berinteraksi dengan objek maya. Sistem realiti tambahan memerlukan penunjuk tertentu, seperti penanda untuk menentukan bagaimana objek maya wujud dalam dunia sebenar. Penunjuk tertentu mesti diperolehi untuk menggunakan sistem realiti tambahan, tetapi susah untuk seseorang mempunyai penunjuk tersebut pada bila-bila masa. Tangan manusia, yang merupakan sebahagian dari badan manusia dapat menyelesaikan masalah ini. Selain itu, tangan boleh digunakan untuk berinteraksi dengan objek maya dalam dunia realiti tambahan. Tesis ini membentangkan sebuah sistem realiti tambahan yang menggunakan tangan terbuka untuk pendaftaran objek maya dalam persekitaran sebenar dan membolehkan pengguna untuk menggunakan tangan yang satu lagi untuk berinteraksi dengan objek maya yang ditambahkan dalam tiga-matra. Untuk menggunakan tangan untuk pendaftaran dan interaksi dalam realiti tambahan, postur dan isyarat tangan pengguna perlu dikesan. The advent of augmented reality (AR) enables virtual objects to be superimposed on the real world and provides a new way to interact with the virtual objects. AR system requires an indicator to determine for how the virtual objects aligned in the real world. The indicator must first be obtained to access to a particular AR system. It may be inconvenient to have the indicator in reach at all time. Human hand, which is part of the human body may be a solution for this. Besides, hand is also a promising tool for interaction with virtual objects in AR environment. This thesis presents a markerless Augmented Reality system which utilizes outstretched hand for registration of virtual objects in the real environment and enables the users to have three dimensional (3D) interaction with the augmented virtual objects. To employ the hand for registration and interaction in AR, hand postures and gestures that the user perform has to be recognized

Computing Cox's smoothing spline score estimator: Working paper series--03-07

We provide an efficient algorithm for computing the smoothing spline score estimator of Cox (1985). The algorithm exploits the banded structure of the linear algebra involved. Calls are made to the LAPACK, Level 1, 2, and 3 BLAS subroutine libraries designed to be efficient on a wide range of modern high-performance computers

Cognitive health of older persons in longitudinal ageing cohort studies

Dementia poses a major global burden of care to society and health systems in ageing populations. The majority (over 60%) of persons with dementia in the world are found in Asia and developing countries with rapid rates of population ageing. Improving and maintaining the cognitive health of older persons is vital to national strategies for dementia prevention. Increasing numbers of population-based ageing cohort studies in the past decade have provided a better understanding of the factors that contribute to cognitive function and decline in old age. The roles of major demographic, psychosocial, lifestyle, behavioral and cardiovascular risk factors contributing to cognitive health were discussed using examples from the Singapore Longitudinal Ageing Studies. They include socio-demographic factors, particularly education and marital status, leisure time activity such as physical activity, social engagement and mental activities, psychological factors such as depression, cardiovascular and metabolic risk factors: obesity, diabetes, hypertension and dyslipidemia, and the metabolic syndrome, under-nutrition, low albumin, low hemoglobin, nutritional factors such as blood folate, B12 and homocysteine, omega-3 poly-unsaturated fatty acids, tea drinking and curcumin-rich turmeric in curry meals. These factors are found to be associated variously with cognitive functions (memory and learning, language, visuospatial, attention and information processing speed), rates of cognitive impairment and cognitive decline, or increased risk of developing MCI and progression to dementia

Reducing high attrition rate in a business statistics course using an interpretive approach encompassing diverse teaching and learning styles: Working paper series--03-11

An interpretive-learner-centered approach is implemented to improve students learning and address the issue of high attrition rate for a business statistics course. It focuses on the interpretation and implications of statistical results through real business problems and data while the mechanical steps of computation via formulae are relegated to the background. The philosophy that "students are responsible for their education" is embraced; thus, a mastery approach to learning was adopted utilizing pre-lecture, post-lecture and lab web quizzes all with multiple attempts allowed. Cooperative learning serves as a common thread in the design through the use of teams in lectures, labs and on two team projects. The projects result in business reports where all statistical jargon is translated into everyday language. Results from data collected on students learning style, pre and post assessments indicate a significant reduction in attrition rate and improved student learning

A sparse implementation of the Frisch-Newton algorithm for 1uantile regression: Working paper series--03-03

Recent experience has shown that interior-point methods using a log barrier approach are far superior to classical simplex methods for computing solutions to large parametric quantile regression problems. In many large empirical applications, the design matrix has a very sparse structure. A typical example is the classical fixed-effect model for panel data where the parametric dimension of the model can be quite large, but the number of non-zero elements is quite small. Adopting recent developments in sparse linear algebra we introduce a modified version of the Frisch-Newton algorithm for quantile regression described in Koenker and Portnoy (1997). The new algorithm substantially reduces the storage (memory) requirements and increases computational speed. The modified algorithm also facilitates the development of nonparametric quantile regression methods. The pseudo design matrices employed in nonparametric quantile regression smoothing are inherently sparse in both the fidelity and roughness penalty components. Exploiting the sparse structure of these problems opens up a whole range of new possibilities for multivariate smoothing on large data sets via ANOVA-type decomposition and partial linear models

The impact of climate change on tourism economies: Working paper series--12-01

Tourism economies depend on tourism for promoting economic growth. Tourism is obviously highly sensitive to climate. Therefore, with mounting evidence of climate change, an important question is: what is the impact of climate change on tourism economies? To answer this question, we use a model in Ng and Zhao (2010) to estimate the economic impacts of climate change on different types of economies. Our main finding is that climate change's impact on tourism economies is not smaller than its impact on other types of economies if temperature increases by more than 1 degree Celsius. Therefore, our findings suggest that tourism economies should also implement aggressive climate mitigation policy