title: Adaptive XGBoost for evolving data streams

authors: Montiel, Jacob

subjects: computer science

abstract: Boosting is an ensemble method that combines base models in a sequential manner to achieve high predictive accuracy. A popular learning algorithm based on this ensemble method is eXtreme Gradient Boosting (XGB). We present an adaptation of XGB for classification of evolving data streams. In this setting, new data arrives over time and the relationship between the class and the features may change in the process, thus exhibiting concept drift. The proposed method creates new members of the ensemble from mini-batches of data as new data becomes available. The maximum ensemble size is fixed, but learning does not stop when this size is reached because the ensemble is updated on new data to ensure consistency with the current concept. We also explore the use of concept drift detection to trigger a mechanism to update the ensemble. We test our method on real and synthetic data with concept drift and compare it against batch-incremental and instance-incremental classification methods for data streams.

text: Adaptive XGBoost for evolving data streams Boosting is an ensemble method that combines base models in a sequential manner to achieve high predictive accuracy. A popular learning algorithm based on this ensemble method is eXtreme Gradient Boosting (XGB). We present an adaptation of XGB for classification of evolving data streams. In this setting, new data arrives over time and the relationship between the class and the features may change in the process, thus exhibiting concept drift. The proposed method creates new members of the ensemble from mini-batches of data as new data becomes available. The maximum ensemble size is fixed, but learning does not stop when this size is reached because the ensemble is updated on new data to ensure consistency with the current concept. We also explore the use of concept drift detection to trigger a mechanism to update the ensemble. We test our method on real and synthetic data with concept drift and compare it against batch-incremental and instance-incremental classification methods for data streams.

year: 2020

title: Human capital, graduate migration and innovation in British regions

authors: Faggian, Alessandra

subjects: graduates

abstract: With the aid of a geographical information system, our paper constructs a three stage least squares simultaneous equation model to investigate the interrelationships between the interregional flows of human capital, and the innovation dynamism of a region. In order to do this, we model the interregional migration behaviour of high quality British university graduates from university into first employment, and we relate these human capital flows to both the labour market characteristics and the knowledge characteristics of the employment regions. This is done for all industries and separately for just high technology industries. Our results indicate that for England and Wales there is a two-way causality between the interregional humancapital employment-migration flows of recent university graduates and the innovation performance of regions. However, the results for Great Britain as a whole depend on whether London is included and Scotland is excluded. We find little or no support for the argument that the presence of local universities or small firms promotes regional innovation.

text: Human capital, graduate migration and innovation in British regions With the aid of a geographical information system, our paper constructs a three stage least squares simultaneous equation model to investigate the interrelationships between the interregional flows of human capital, and the innovation dynamism of a region. In order to do this, we model the interregional migration behaviour of high quality British university graduates from university into first employment, and we relate these human capital flows to both the labour market characteristics and the knowledge characteristics of the employment regions. This is done for all industries and separately for just high technology industries. Our results indicate that for England and Wales there is a two-way causality between the interregional humancapital employment-migration flows of recent university graduates and the innovation performance of regions. However, the results for Great Britain as a whole depend on whether London is included and Scotland is excluded. We find little or no support for the argument that the presence of local universities or small firms promotes regional innovation.

year: 2009

title: Breaking the Barrier: Maori religious and spiritual entanglements at Aotea

authors: Klink, Kelly Moanna

subjects: Ngati Rehua

abstract: In 1889, Ngāti Rehua converted en masse to the Church of Jesus Christ of Latter Day Saints (LDS). This surprising conversion is remarkable for various reasons.  Māori across the country had not only converted to Christianity several decades earlier but by the late nineteenth century had already established their own religious denominations that renegotiated Judeao Christian teachings in new ways.  The proximity of Aotea to the Bay of Islands and their own converted kin on the mainland made this very late conversion all the more remarkable. This was the first time that any Christian organisation found any meaningful success with native peoples on the island, despite the widespread impact of Anglican, Catholic, Wesleyan, and Presbyterian missionaries throughout the region. With so many converted iwi at their doorstep, and the widespread influence of early missionaries and Māori agents of conversion, why did Ngāti Rehua take so long to convert to Christianity? While other iwi were converting in large numbers to Christianity or renegotiating Christianity on their own terms, Ngāti Rehua remained isolated and aloof for much of the nineteenth century, maintaining traditional beliefs and practices that had disappeared or been significantly modified in other tribal regions.  This thesis explores this question in three main chapters. Chapter One explores early Aotea history, beliefs and practices and examines how those on the island remained elusive from the onslaught of missionaries during the formative years of the establishment of Christianity.  Chapter Two highlights the many Aotea inter-tribal connections, the ongoing isolated history of Aotea and early missionary influences. Chapter Three turns its attention to the arrival of Mormon missionaries in 1889 and discusses the ‘moments’ of conversion that have been maintained in successive generations.

text: Breaking the Barrier: Maori religious and spiritual entanglements at Aotea In 1889, Ngāti Rehua converted en masse to the Church of Jesus Christ of Latter Day Saints (LDS). This surprising conversion is remarkable for various reasons.  Māori across the country had not only converted to Christianity several decades earlier but by the late nineteenth century had already established their own religious denominations that renegotiated Judeao Christian teachings in new ways.  The proximity of Aotea to the Bay of Islands and their own converted kin on the mainland made this very late conversion all the more remarkable. This was the first time that any Christian organisation found any meaningful success with native peoples on the island, despite the widespread impact of Anglican, Catholic, Wesleyan, and Presbyterian missionaries throughout the region. With so many converted iwi at their doorstep, and the widespread influence of early missionaries and Māori agents of conversion, why did Ngāti Rehua take so long to convert to Christianity? While other iwi were converting in large numbers to Christianity or renegotiating Christianity on their own terms, Ngāti Rehua remained isolated and aloof for much of the nineteenth century, maintaining traditional beliefs and practices that had disappeared or been significantly modified in other tribal regions.  This thesis explores this question in three main chapters. Chapter One explores early Aotea history, beliefs and practices and examines how those on the island remained elusive from the onslaught of missionaries during the formative years of the establishment of Christianity.  Chapter Two highlights the many Aotea inter-tribal connections, the ongoing isolated history of Aotea and early missionary influences. Chapter Three turns its attention to the arrival of Mormon missionaries in 1889 and discusses the ‘moments’ of conversion that have been maintained in successive generations.

year: 2019