title: Stacked generalization: when does it work?

authors: Ting, Kai Ming

subjects: stacking

abstract: Stacked generalization is a general method of using a high-level model to combine lower-level models to achieve greater predictive accuracy. In this paper we resolve two crucial issues which have been considered to be a ‘black art’ in classification tasks ever since the introduction of stacked generalization in 1992 by Wolpert: the type of generalizer that is suitable to derive the higher-level model, and the kind of attributes that should be used as its input. 
We demonstrate the effectiveness of stacked generalization for combining three different types of learning algorithms, and also for combining models of the same type derived from a single learning algorithm in a multiple-data-batches scenario. We also compare the performance of stacked generalization with published results of arcing and bagging.

text: Stacked generalization: when does it work? Stacked generalization is a general method of using a high-level model to combine lower-level models to achieve greater predictive accuracy. In this paper we resolve two crucial issues which have been considered to be a ‘black art’ in classification tasks ever since the introduction of stacked generalization in 1992 by Wolpert: the type of generalizer that is suitable to derive the higher-level model, and the kind of attributes that should be used as its input. 
We demonstrate the effectiveness of stacked generalization for combining three different types of learning algorithms, and also for combining models of the same type derived from a single learning algorithm in a multiple-data-batches scenario. We also compare the performance of stacked generalization with published results of arcing and bagging.

year: 1997-01

title: Enhancement of the Hooghoudt Drain-Spacing Equation

authors: Shokri, Ali

subjects: Science & Technology

abstract: The Hooghoudt equation is widely used as a simple means of specifying drain spacing when designing networks of parallel drains in drainage systems, based on estimating the maximum water table height between two drains. It is shown via comparison with a numerical model that the Hooghoudt equation can overestimate water table height and therefore yield drain spacings that may be too wide. This is because the Hooghoudt drain-spacing equation in fact has a concealed dependency on Van Genuchten soil-water retention curve parameters, which can bias the water table estimates unless adjustments are made explicitly. A modification of the Hooghoudt equation is presented that incorporates two new dimensionless coefficients to make allowance for this dependency. The modified expression yields improved accuracy as measured against the numerical reference model.

text: Enhancement of the Hooghoudt Drain-Spacing Equation The Hooghoudt equation is widely used as a simple means of specifying drain spacing when designing networks of parallel drains in drainage systems, based on estimating the maximum water table height between two drains. It is shown via comparison with a numerical model that the Hooghoudt equation can overestimate water table height and therefore yield drain spacings that may be too wide. This is because the Hooghoudt drain-spacing equation in fact has a concealed dependency on Van Genuchten soil-water retention curve parameters, which can bias the water table estimates unless adjustments are made explicitly. A modification of the Hooghoudt equation is presented that incorporates two new dimensionless coefficients to make allowance for this dependency. The modified expression yields improved accuracy as measured against the numerical reference model.

year: 2015-06-01

title: The day ahead

authors: Webber, Warren

abstract: With a professional background in agriculture and veterinary science, and a decade of participation in water quality issues for the Rotorua Lakes catchments, Warren brings an intense personal, but non-vested interest, to issues of nutrient management on the land and in our waterways. Conference management (international and domestic) helps to pay the bills, but voluntary community interests take up much of his time. As an appointee to the Stakeholder Advisory Group (StAG) which considers land management and land use change policy issues on behalf of the Te Arawa Lakes Strategy Group, he is closely involved with the challenges of nutrient allocation and incentives for change.

text: The day ahead With a professional background in agriculture and veterinary science, and a decade of participation in water quality issues for the Rotorua Lakes catchments, Warren brings an intense personal, but non-vested interest, to issues of nutrient management on the land and in our waterways. Conference management (international and domestic) helps to pay the bills, but voluntary community interests take up much of his time. As an appointee to the Stakeholder Advisory Group (StAG) which considers land management and land use change policy issues on behalf of the Te Arawa Lakes Strategy Group, he is closely involved with the challenges of nutrient allocation and incentives for change.

year: 2013