title: Having a Blast: Meta-Learning and Heterogeneous Ensembles for Data Streams

authors: van Rijn, Jan N.

subjects: Science & Technology

abstract: Ensembles of classifiers are among the best performing classifiers available in many data mining applications. However, most ensembles developed specifically for the dynamic data stream setting rely on only one type of base-level classifier, most often Hoeffding Trees. In this paper, we study the use of heterogeneous ensembles, comprised of fundamentally different model types. Heterogeneous ensembles have proven successful in the classical batch data setting, however they do not easily transfer to the data stream setting. We therefore introduce the Online Performance Estimation framework, which can be used in data stream ensembles to weight the votes of (heterogeneous) ensemble members differently across the stream. Experiments over a wide range of data streams show performance that is competitive with state of the art ensemble techniques, including Online Bagging and Leveraging Bagging. All experimental results from this work are easily reproducible and publicly available on OpenML for further analysis.

text: Having a Blast: Meta-Learning and Heterogeneous Ensembles for Data Streams Ensembles of classifiers are among the best performing classifiers available in many data mining applications. However, most ensembles developed specifically for the dynamic data stream setting rely on only one type of base-level classifier, most often Hoeffding Trees. In this paper, we study the use of heterogeneous ensembles, comprised of fundamentally different model types. Heterogeneous ensembles have proven successful in the classical batch data setting, however they do not easily transfer to the data stream setting. We therefore introduce the Online Performance Estimation framework, which can be used in data stream ensembles to weight the votes of (heterogeneous) ensemble members differently across the stream. Experiments over a wide range of data streams show performance that is competitive with state of the art ensemble techniques, including Online Bagging and Leveraging Bagging. All experimental results from this work are easily reproducible and publicly available on OpenML for further analysis.

year: 2015-01-01

title: What happens to diet and child health when migration splits households? Evidence from a migration lottery program

authors: Gibson, John

subjects: migration

abstract: The impact of migration on food security and child health is likely to differ depending on whether children themselves migrate or whether they remain behind while other household members migrate. However, existing studies have not been able to examine how impacts differ in these two scenarios because parallel data are required for both the sending and receiving country. Moreover, self-selection into migration makes unbiased estimation of either impact difficult. We overcome these problems by using a unique survey of Tongan households that applied to migrate to New Zealand through a migrant quota which selects households through a random ballot. This survey covers both migrant children in New Zealand and non-migrant children in Tonga, with the migration policy rules providing a source of exogenous variation for identifying impacts. Our estimates of short-run impacts show that diets diverge upon migration: children who migrate experience improvements, while diets worsen for children who remain. There is also suggestive evidence of a divergence in health outcomes, with increases in weight-for-age and height-for-age found for migrant children, and decreases found for children who remain behind while other household members migrate.

text: What happens to diet and child health when migration splits households? Evidence from a migration lottery program The impact of migration on food security and child health is likely to differ depending on whether children themselves migrate or whether they remain behind while other household members migrate. However, existing studies have not been able to examine how impacts differ in these two scenarios because parallel data are required for both the sending and receiving country. Moreover, self-selection into migration makes unbiased estimation of either impact difficult. We overcome these problems by using a unique survey of Tongan households that applied to migrate to New Zealand through a migrant quota which selects households through a random ballot. This survey covers both migrant children in New Zealand and non-migrant children in Tonga, with the migration policy rules providing a source of exogenous variation for identifying impacts. Our estimates of short-run impacts show that diets diverge upon migration: children who migrate experience improvements, while diets worsen for children who remain. There is also suggestive evidence of a divergence in health outcomes, with increases in weight-for-age and height-for-age found for migrant children, and decreases found for children who remain behind while other household members migrate.

year: 2010

title: Pushing the process: A whānau journey through the Treaty of Waitangi claims process

authors: Harrison, Reece David

subjects: Whanau Claims

abstract: This thesis follows the journey of a Whānau (ngā uri a Arama Whakatau) in its Claim to the Waitangi Tribunal under the Treaty of Waitangi Act 1986. In particular, it looks at inter-Whānau dynamics before, during and after the Claims process. The connections to the claimant area through whakapapa and establishing ahi kaa rights are identified, as are problems faced by lodging a Claim at the Whānau level. Aspects of inter-Whānau, inter-Hapū and inter-iwi politics are considered along with Crown agencies' processes. The primary question posed in the thesis is whether a Whānau Claim is the more appropriate avenue compared to making a Claim through the Hapū or iwi. However, the inter-Whānau dynamics are the core focus of the thesis in this 'warts-and-all' discussion from the perspective of the participant-observer.

text: Pushing the process: A whānau journey through the Treaty of Waitangi claims process This thesis follows the journey of a Whānau (ngā uri a Arama Whakatau) in its Claim to the Waitangi Tribunal under the Treaty of Waitangi Act 1986. In particular, it looks at inter-Whānau dynamics before, during and after the Claims process. The connections to the claimant area through whakapapa and establishing ahi kaa rights are identified, as are problems faced by lodging a Claim at the Whānau level. Aspects of inter-Whānau, inter-Hapū and inter-iwi politics are considered along with Crown agencies' processes. The primary question posed in the thesis is whether a Whānau Claim is the more appropriate avenue compared to making a Claim through the Hapū or iwi. However, the inter-Whānau dynamics are the core focus of the thesis in this 'warts-and-all' discussion from the perspective of the participant-observer.

year: 2007