4,252 research outputs found
The Baker-Akhiezer function and factorization of the Chebotarev-Khrapkov matrix
A new technique is proposed for the solution of the Riemann-Hilbert problem
with the Chebotarev-Khrapkov matrix coefficient
, ,
is a zero-trace polynomial matrix, and is the unit matrix. This
problem has numerous applications in elasticity and diffraction theory. The
main feature of the method is the removal of the essential singularities of the
solution to the associated homogeneous scalar Riemann-Hilbert problem on the
hyperelliptic surface of an algebraic function by means of the Baker-Akhiezer
function. The consequent application of this function for the derivation of the
general solution to the vector Riemann-Hilbert problem requires finding of the
zeros of the Baker-Akhiezer function ( is the genus of the
surface). These zeros are recovered through the solution to the associated
Jacobi problem of inversion of abelian integrals or, equivalently, the
determination of the zeros of the associated degree- polynomial and
solution of a certain linear algebraic system of equations.Comment: 17 pages, 1 figur
Applying CHAID for logistic regression diagnostics and classification accuracy improvement
In this study a CHAID-based approach to detecting classification accuracy heterogeneity across segments of observations is proposed. This helps to solve some important problems, facing a model-builder: 1. How to automatically detect segments in which the model significantly underperforms? 2. How to incorporate the knowledge about classification accuracy heterogeneity across segments to partition observations in order to achieve better predictive accuracy? The approach was applied to churn data from the UCI Repository of Machine Learning Databases. By splitting the dataset into 4 parts, which are based on the decision tree, and building a separate logistic regression scoring model for each segment we increased the accuracy by more than 7 percentage points on the test sample. Significant increase in recall and precision was also observed. It was shown that different segments may have absolutely different churn predictors. Therefore such a partitioning gives a better insight into factors influencing customer behavior.CHAID; logistic regression; churn prediction; performance improvement; segmentwise prediction; decision tree; classification tree
Applying a CART-based approach for the diagnostics of mass appraisal models
In this paper an approach for automatic detection of segments where a regression model significantly underperforms and for detecting segments with systematically under- or overestimated prediction is introduced. This segmentational approach is applicable to various expert systems including, but not limited to, those used for the mass appraisal. The proposed approach may be useful for various regression analysis applications, especially those with strong heteroscedasticity. It helps to reveal segments for which separate models or appraiser assistance are desirable. The segmentational approach has been applied to a mass appraisal model based on the Random Forest algorithm.CART, model diagnostics, mass appraisal, real estate, Random forest, heteroscedasticity
Mass appraisal of residential apartments: An application of Random forest for valuation and a CART-based approach for model diagnostics
To the best knowledge of authors, the use of Random forest as a potential technique for residential estate mass appraisal has been attempted for the first time. In the empirical study using data on residential apartments the method performed better than such techniques as CHAID, CART, KNN, multiple regression analysis, Artificial Neural Networks (MLP and RBF) and Boosted Trees. An approach for automatic detection of segments where a model significantly underperforms and for detecting segments with systematically under- or overestimated prediction is introduced. This segmentational approach is applicable to various expert systems including, but not limited to, those used for the mass appraisal.Random forest, mass appraisal, CART, model diagnostics, real estate, automatic valuation model
- β¦