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How to down-weight observations in robust regression: A metalearning study
Kalina, Jan; Pitra, Zbyněk
2018 - anglický
Metalearning is becoming an increasingly important methodology for extracting knowledge from a data base of available training data sets to a new (independent) data set. The concept of metalearning is becoming popular in statistical learning and there is an increasing number of metalearning applications also in the analysis of economic data sets. Still, not much attention has been paid to its limitations and disadvantages. For this purpose, we use various linear regression estimators (including highly robust ones) over a set of 30 data sets with economic background and perform a metalearning study over them as well as over the same data sets after an artificial contamination. We focus on comparing the prediction performance of the least weighted squares estimator with various weighting schemes. A broader spectrum of classification methods is applied and a support vector machine turns out to yield the best results. While results of a leave-1-out cross validation are very different from results of autovalidation, we realize that metalearning is highly unstable and its results should be interpreted with care. We also focus on discussing all possible limitations of the metalearning methodology in general. Klíčová slova: metalearning; robust statistics; linear regression; outliers Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
How to down-weight observations in robust regression: A metalearning study

Metalearning is becoming an increasingly important methodology for extracting knowledge from a data base of available training data sets to a new (independent) data set. The concept of metalearning is ...

Kalina, Jan; Pitra, Zbyněk
Ústav informatiky, 2018

Soupis publikovaých prací pana prof. Ing. Mirko Nováka, DrSc. zpracovaný ke dni 13. dubna 2018 knihovnou Ústavu informatiky AV ČR, v. v. i. s ohledem na dostupnost uvedených prací
Nývltová, Ludmila; Ramešová, Nina; Šírová, Tereza
2018 - český
Klíčová slova: bibliografie Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Soupis publikovaých prací pana prof. Ing. Mirko Nováka, DrSc. zpracovaný ke dni 13. dubna 2018 knihovnou Ústavu informatiky AV ČR, v. v. i. s ohledem na dostupnost uvedených prací

Nývltová, Ludmila; Ramešová, Nina; Šírová, Tereza
Ústav informatiky, 2018

Numerical solution of generalized minimax problems
Lukšan, Ladislav; Matonoha, Ctirad; Vlček, Jan
2018 - anglický
Klíčová slova: Numerical optimization; nonlinear approximation; nonsmooth optimization; generalized minimax problems; recursive quadratic programming methods; interior point methods; smoothing methods; algorithms; numerical experiments Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Numerical solution of generalized minimax problems

Lukšan, Ladislav; Matonoha, Ctirad; Vlček, Jan
Ústav informatiky, 2018

A limited-memory optimization method using the infinitely many times repeated BNS update and conjugate directions
Vlček, Jan; Lukšan, Ladislav
2018 - anglický
Klíčová slova: Unconstrained minimization; variable metric methods; limited-memory methods; the repeated BFGS update; global convergence; numerical results Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
A limited-memory optimization method using the infinitely many times repeated BNS update and conjugate directions

Vlček, Jan; Lukšan, Ladislav
Ústav informatiky, 2018

Semigroup Structure of Sets of Solutions to Equation X^s = X^m
Porubský, Štefan
2017 - anglický
Using an idempotent semigroup approach we describe the semigroup and group structure of the set of solutions to equation X^m = X^s in successive steps over a periodic commutative semigroup, over multiplicative semigroups of factor rings of residually finite commutative rings and finally over multiplicative semigroups of factor rings of residually finite commutative principal ideal domains. The analysis is done through the use of the maximal subsemigroups and groups corresponding to an idempotent of the corresponding semigroup and in the case of residually finite PID’s employing the available analysis of the Euler-Fermat Theorem as given in [11]. In particular the case when this set of solutions is a union of groups is handled. As a simple application we show a not yet noticed group structure of the set of solutions to x^n = x connected with the message space of RSA cryptosystems and Fermat pseudoprimes. Klíčová slova: set of solutions; idempotent; maximal semigroup corresponding to an idempotent; maximal group corresponding to an idempotent; equation X^s = X^m; finite commutative ring with identity element; residually finite commutative principal ideal domains Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Semigroup Structure of Sets of Solutions to Equation X^s = X^m

Using an idempotent semigroup approach we describe the semigroup and group structure of the set of solutions to equation X^m = X^s in successive steps over a periodic commutative semigroup, over ...

Porubský, Štefan
Ústav informatiky, 2017

Návrh integrovaného emisního procesoru nové generace
Resler, Jaroslav; Juruš, Pavel; Benešová, N.; Vlček, O.; Belda, M.; Huszár, P.; Krč, Pavel; Eben, Kryštof
2017 - český
V podstatě jediným rozšířeným a veřejně dostupným nástrojem pro modelování emisí pro potřeby CTM je procesor SMOKE (Coats & Carlie, 1996). Problém modelu SMOKE ovšem je v jeho silné vazbě na podmínky USA. V minulosti došlo k několika pokusům uzpůsobit model SMOKE jiným podmínkám - viz např. práce reportované v Bieser et al., 2011 nebo Borge et al., 2008, úsilí ovšem vždy naráželo na limity designu tohoto emisního procesoru. Naším cílem je vyvinout emisní procesor založený na otevřených technologiích, který bude komfortní pro typické využití v CTM v našich podmínkách a který bude dostatečně flexibilní, aby byl snadno konfigurovatelný a nastavitelný i pro ostatní uživatele ve světě a jejich specifické potřeby. The only publicly available and widely used tool for emission modelling for CTM is the processor SMOKE (Coats & Carlie, 1996), but its usage is limited by its strong dependence on conditions of USA. A few attempts to adjust SMOKE to other conditions were made in the past - see e.g. works reported in Bieser et al., 2011 or Borge et al., 2008, but the efforts hit the limits of its design. Our goal is to develop an emission processor based on open technologies which will be easy to use for typical usage with CTM in our conditions and which will be flexible and configurable enough to serve specific needs of users in other countries over the world. Klíčová slova: emission model; CTM; postgresql; postgis; inventory Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Návrh integrovaného emisního procesoru nové generace

V podstatě jediným rozšířeným a veřejně dostupným nástrojem pro modelování emisí pro potřeby CTM je procesor SMOKE (Coats & Carlie, 1996). Problém modelu SMOKE ovšem je v jeho silné vazbě na podmínky ...

Resler, Jaroslav; Juruš, Pavel; Benešová, N.; Vlček, O.; Belda, M.; Huszár, P.; Krč, Pavel; Eben, Kryštof
Ústav informatiky, 2017

An adaptive recursive multilevel approximate inverse preconditioning: Computation of the Schur complement
Kopal, Jiří; Rozložník, Miroslav; Tůma, Miroslav
2017 - anglický
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
An adaptive recursive multilevel approximate inverse preconditioning: Computation of the Schur complement

Kopal, Jiří; Rozložník, Miroslav; Tůma, Miroslav
Ústav informatiky, 2017

The Computational Power of Neural Networks and Representations of Numbers in Non-Integer Bases.
Šíma, Jiří
2017 - anglický
We briefly survey the basic concepts and results concerning the computational power of neural networks which basically depends on the information content of weight parameters. In particular, recurrent neural networks with integer, rational, and arbitrary real weights are classified within the Chomsky and finer complexity hierarchies. Then we refine the analysis between integer and rational weights by investigating an intermediate model of integer-weight neural networks with an extra analog rational-weight neuron (1ANN). We show a representation theorem which characterizes the classification problems solvable by 1ANNs, by using so-called cut languages. Our analysis reveals an interesting link to an active research field on non-standard positional numeral systems with non-integer bases. Within this framework, we introduce a new concept of quasi-periodic numbers which is used to classify the computational power of 1ANNs within the Chomsky hierarchy. Klíčová slova: neural network; Chomsky hierarchy; beta-expansion; cut language Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The Computational Power of Neural Networks and Representations of Numbers in Non-Integer Bases.

We briefly survey the basic concepts and results concerning the computational power of neural networks which basically depends on the information content of weight parameters. In particular, recurrent ...

Šíma, Jiří
Ústav informatiky, 2017

Exact Inference In Robust Econometrics under Heteroscedasticity
Kalina, Jan; Peštová, Barbora
2017 - anglický
The paper is devoted to the least weighted squares estimator, which is one of highly robust estimators for the linear regression model. Novel permutation tests of heteroscedasticity are proposed. Also the asymptotic behavior of the permutation test statistics of the Goldfeld-Quandt and Breusch-Pagan tests is investigated. A numerical experiment on real economic data is presented, which also shows how to perform a robust prediction model under heteroscedasticity. Theoretical results may be simply extended to the context of multivariate quantiles Klíčová slova: heteroscedasticity; robust statistics; regression; diagnostic tools; economic data Dokument je dostupný na externích webových stránkách.
Exact Inference In Robust Econometrics under Heteroscedasticity

The paper is devoted to the least weighted squares estimator, which is one of highly robust estimators for the linear regression model. Novel permutation tests of heteroscedasticity are proposed. Also ...

Kalina, Jan; Peštová, Barbora
Ústav informatiky, 2017

Idempotents, Group Membership and their Applications
Porubský, Štefan
2017 - anglický
S.Schwarz in his paper [165] proved the existence of maximal subgroups in periodic semigroups and a decade later he brought [167] into play the maximal subsemigroups and thus he embodied the idempotents in the structural description of semigroups. Later in his papers he showed that a proper description of these structural elements can be used to (re)prove many useful and important results in algebra and number theory. The present paper gives a survey of selected results scattered throughout the literature where an semigroup approach based on tools like idempotent, maximal subgroup or maximal subsemigroup either led to a new insight into the substance of the known results or helped to discover new approach to solve problems. Special attention will be given to some disregarded historical connections between semigroup and ring theory. Klíčová slova: multiplicative semigroup; finite semigroups; power semigroups; idempotent elements; finite commutative rings; principal ideal domain; Euler-Fermat theorem; Wilson theorem; matrices over fields; maximal groups contained in a semigroup; periodic sequence; multiplicative semigroup of Zm; semigroup of circulant Boolean matrices Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Idempotents, Group Membership and their Applications

S.Schwarz in his paper [165] proved the existence of maximal subgroups in periodic semigroups and a decade later he brought [167] into play the maximal subsemigroups and thus he embodied the ...

Porubský, Štefan
Ústav informatiky, 2017

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