title: Accurate Ensembles for Data Streams: Combing Restricted Hoeffding Trees using Stacking

authors: Bifet, Albert

subjects: Science & Technology

abstract: The success of simple methods for classification shows that it is often not necessary to model complex attribute interactions to obtain good classification accuracy on practical problems. In this paper, we propose to exploit this phenomenon in the data stream context by building an ensemble of Hoeffding trees that are each limited to a small subset of attributes. In this way, each tree is restricted to model interactions between attributes in its corresponding subset. Because it is not known a priori which attribute subsets are relevant for prediction, we build exhaustive ensembles that consider all possible attribute subsets of a given size. As the resulting Hoeffding trees are not all equally important, we weight them in a suitable manner to obtain accurate classifications. This is done by combining the log-odds of their probability estimates using sigmoid perceptrons, with one perceptron per class. We propose a mechanism for setting the perceptrons’ learning rate using the ADWIN change detection method for data streams and also use ADWIN to reset ensemble members (i.e., Hoeffding trees) when they no longer perform well. Our experiments show that the resulting ensemble classifier outperforms bagging for data streams in terms of accuracy when both are used in conjunction with adaptive naive Bayes Hoeffding trees, at the expense of runtime and memory consumption.

text: Accurate Ensembles for Data Streams: Combing Restricted Hoeffding Trees using Stacking The success of simple methods for classification shows that it is often not necessary to model complex attribute interactions to obtain good classification accuracy on practical problems. In this paper, we propose to exploit this phenomenon in the data stream context by building an ensemble of Hoeffding trees that are each limited to a small subset of attributes. In this way, each tree is restricted to model interactions between attributes in its corresponding subset. Because it is not known a priori which attribute subsets are relevant for prediction, we build exhaustive ensembles that consider all possible attribute subsets of a given size. As the resulting Hoeffding trees are not all equally important, we weight them in a suitable manner to obtain accurate classifications. This is done by combining the log-odds of their probability estimates using sigmoid perceptrons, with one perceptron per class. We propose a mechanism for setting the perceptrons’ learning rate using the ADWIN change detection method for data streams and also use ADWIN to reset ensemble members (i.e., Hoeffding trees) when they no longer perform well. Our experiments show that the resulting ensemble classifier outperforms bagging for data streams in terms of accuracy when both are used in conjunction with adaptive naive Bayes Hoeffding trees, at the expense of runtime and memory consumption.

year: 2010-01-01

title: Environmental effects of ozone depletion and its interactions with climate change: progress report, 2009

authors: Andrady, Anthony

subjects: UV

abstract: The parties to the Montreal Protocol are informed by three panels of experts. One of these is the Environmental Effects Assessment Panel (EEAP), which deals with UV radiation and its effects on human health, animals, plants, biogeochemistry, air quality and materials. Since 2000, the analyses and interpretation of these effects have included interactions between UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than believed previously. As a result of this, human health and environmental problems will likely be longer-lasting and more regionally variable. Like the other panels, the EEAP produces a detailed report every four years; the most recent was that for 2006 (Photochem. Photobiol. Sci., 2007, 6, 201–332). In the years in between, the EEAP produces a less detailed and shorter progress report, as is the case for this present one for 2009. A full quadrennial report will follow for 2010.

text: Environmental effects of ozone depletion and its interactions with climate change: progress report, 2009 The parties to the Montreal Protocol are informed by three panels of experts. One of these is the Environmental Effects Assessment Panel (EEAP), which deals with UV radiation and its effects on human health, animals, plants, biogeochemistry, air quality and materials. Since 2000, the analyses and interpretation of these effects have included interactions between UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than believed previously. As a result of this, human health and environmental problems will likely be longer-lasting and more regionally variable. Like the other panels, the EEAP produces a detailed report every four years; the most recent was that for 2006 (Photochem. Photobiol. Sci., 2007, 6, 201–332). In the years in between, the EEAP produces a less detailed and shorter progress report, as is the case for this present one for 2009. A full quadrennial report will follow for 2010.

year: 2010

title: Maori perspectives of the environment: A review of resource use consent submissions made by iwi to Environment Waikato.

authors: Whangapirita, Laura

subjects: Maori

abstract: As part of our broader brief to gather, summarise, analyse and distribute information held by Environment Waikato on Maori and the environment, we reviewed and summarised iwi consent submissions made on various resource use consent applications. This report refers to values and beliefs sourced from iwi submissions held by Environment Waikato and are presented within a Maori values framework to highlight environmental perspectives of tangata whenua in the Waikato region.

text: Maori perspectives of the environment: A review of resource use consent submissions made by iwi to Environment Waikato. As part of our broader brief to gather, summarise, analyse and distribute information held by Environment Waikato on Maori and the environment, we reviewed and summarised iwi consent submissions made on various resource use consent applications. This report refers to values and beliefs sourced from iwi submissions held by Environment Waikato and are presented within a Maori values framework to highlight environmental perspectives of tangata whenua in the Waikato region.

year: 2003-11