sábado, 12 de marzo de 2016
Algoritmos genéticos
Esta cita de Darwin resume en una frase el funcionamiento de los algoritmos genéticos.
domingo, 27 de diciembre de 2015
Probabilidad de empate
En relación al empate que hoy se ha producido en la asamblea de la CUP, lamentamos tener que desmentir afirmaciones como esta:
La probabilidad de que se haya producido este empate no es tan baja como indica Mario Bilbao. La probabilidad de que determinado número de asistentes a la asamblea vote por la investidura de Mas es función de la probabilidad p de que cada uno de los miembros de la asamblea desee investir presidente a Mas: los resultados habrían sido muy distintos si todos los asistentes estuvieran convencidos de investir a Mas (p próxima a 1) o de no investirlo (p próxima a 0). Para determinar la probabilidad de que exactamente 1515 de los 3030 asistentes hayan votado por la investidura de Mas, hemos de utilizar la distribución de probabilidad binomial.
El siguiente gráfico muestra la probabilidad de que se produzca empate (prob) en función de la probabilidad de que un miembro de la asamblea desee que Mas sea investido (p):
Como Antoni Ítalo (entre otros) ha indicado, la probabilidad de empate es como máximo del 1,45%, y es (ahora sí) prácticamente despreciable si p no está entre 0,47 y 0,52 aproximadamente.
La probabilidad de que se haya producido este empate no es tan baja como indica Mario Bilbao. La probabilidad de que determinado número de asistentes a la asamblea vote por la investidura de Mas es función de la probabilidad p de que cada uno de los miembros de la asamblea desee investir presidente a Mas: los resultados habrían sido muy distintos si todos los asistentes estuvieran convencidos de investir a Mas (p próxima a 1) o de no investirlo (p próxima a 0). Para determinar la probabilidad de que exactamente 1515 de los 3030 asistentes hayan votado por la investidura de Mas, hemos de utilizar la distribución de probabilidad binomial.
El siguiente gráfico muestra la probabilidad de que se produzca empate (prob) en función de la probabilidad de que un miembro de la asamblea desee que Mas sea investido (p):
Como Antoni Ítalo (entre otros) ha indicado, la probabilidad de empate es como máximo del 1,45%, y es (ahora sí) prácticamente despreciable si p no está entre 0,47 y 0,52 aproximadamente.
lunes, 16 de noviembre de 2015
The Spanish corporate structure through interlocking directorates
Citation
Sicilia, Carlos; Sallan, Jose M.; Simo, Pep (2016). The Spanish corporate structure through interlocking directorates. Cuadernos de Gestión, 63(1):63-84.
DOI: http://dx.doi.org/10.5295/cdg.120336ps
Abstract
The objective of this paper is to determine to what extent globalisation pressures are changing networks modelled on continental capitalism into Anglo-Saxon models. For this purpose we analyse the Spanish network of interlocks, comparing the present structure with that of 1993. We show how, although Spanish corporative structure continues to display characteristics of the continental economies, some major banks are significantly reducing industrial activity. Nevertheless, the financial organisations continue to maintain a close relationship with sectors such as construction and services. According to the theories on the role of the interlocking directorates, the companies in these sectors assure their access to banking credit by incorporating advisors from financial organisations to their board of directors.
El objetivo de este trabajo es determinar en qué medida las presiones de la globalización han cambiado los modelos que siguen las redes corporativas españolas desde los propios del capitalismo continental hacia los modelos anglosajones. Para ello se analiza la red española de consejerías cruzadas, comparando la estructura actual con la de 1993. Se muestra cómo, a pesar de la estructura corporativa española continúa mostrando características de las economías continentales, algunos de los principales bancos están reduciendo significativamente la actividad industrial. No obstante, las entidades financieras siguen manteniendo una estrecha relación con sectores como la construcción y los servicios. De acuerdo con las teorías sobre el papel de las consejerías cruzadas, las empresas de estos sectores tratan de asegurar su acceso al crédito bancario mediante la incorporación de asesores de las entidades financieras a su consejo de administración.
Sicilia, Carlos; Sallan, Jose M.; Simo, Pep (2016). The Spanish corporate structure through interlocking directorates. Cuadernos de Gestión, 63(1):63-84.
DOI: http://dx.doi.org/10.5295/cdg.120336ps
Abstract
The objective of this paper is to determine to what extent globalisation pressures are changing networks modelled on continental capitalism into Anglo-Saxon models. For this purpose we analyse the Spanish network of interlocks, comparing the present structure with that of 1993. We show how, although Spanish corporative structure continues to display characteristics of the continental economies, some major banks are significantly reducing industrial activity. Nevertheless, the financial organisations continue to maintain a close relationship with sectors such as construction and services. According to the theories on the role of the interlocking directorates, the companies in these sectors assure their access to banking credit by incorporating advisors from financial organisations to their board of directors.
El objetivo de este trabajo es determinar en qué medida las presiones de la globalización han cambiado los modelos que siguen las redes corporativas españolas desde los propios del capitalismo continental hacia los modelos anglosajones. Para ello se analiza la red española de consejerías cruzadas, comparando la estructura actual con la de 1993. Se muestra cómo, a pesar de la estructura corporativa española continúa mostrando características de las economías continentales, algunos de los principales bancos están reduciendo significativamente la actividad industrial. No obstante, las entidades financieras siguen manteniendo una estrecha relación con sectores como la construcción y los servicios. De acuerdo con las teorías sobre el papel de las consejerías cruzadas, las empresas de estos sectores tratan de asegurar su acceso al crédito bancario mediante la incorporación de asesores de las entidades financieras a su consejo de administración.
sábado, 19 de septiembre de 2015
Combinatorial explosion
Combinatorial optimization is about picking one element of a set of finite objects that optimizes an objective function. Put in this way, the solution may seem straightforward: just enumerate all elements of the set and assess the objective function for each object.
The problem with this naïve approach is that the number of elements of the set can be very large. Let's consider, for instance, the symmetric travelling salesperson problem. For an instance of n nodes, the number of possible solutions is the factorial of (n-1) divided by two. This means that, for a problem of size n=20, and taking one millisecond to assess each solution, it takes around 1,108,606 years to assess all solutions. This effect is called combinatorial explosion.
This video shows an example of an even faster combinatorial explosion. Additionally, helps in learning how to count large numbers in Japanese...
The problem with this naïve approach is that the number of elements of the set can be very large. Let's consider, for instance, the symmetric travelling salesperson problem. For an instance of n nodes, the number of possible solutions is the factorial of (n-1) divided by two. This means that, for a problem of size n=20, and taking one millisecond to assess each solution, it takes around 1,108,606 years to assess all solutions. This effect is called combinatorial explosion.
This video shows an example of an even faster combinatorial explosion. Additionally, helps in learning how to count large numbers in Japanese...
viernes, 11 de septiembre de 2015
Modeling and Solving Linear Programming with R
Citation
Sallan, Jose M.; Lordan, Oriol; Fernandez, Vicenc (2015). Modeling and Solving Linear Programming with R. Omniascience.
Abstract
Linear programming is one of the most extensively used techniques in the toolbox of quantitative methods of optimization. One of the reasons of the popularity of linear programming is that it allows to model a large variety of situations with a simple framework. Furthermore, a linear program is relatively easy to solve. The simplex method allows to solve most linear programs efficiently, and the Karmarkar interior-point method allows a more efficient solving of some kinds of linear programming. The power of linear programming is greatly enhanced when came the opportunity of solving integer and mixed integer linear programming. In these models all or some of the decision variables are integers, respectively.
In this book we provide a brief introduction to linear programming, together with a set of exercises that introduce some applications of linear programming. We will also provide an introduction to solve linear programming in R. For each problem a possible solution through linear programming is introduced, together with the code to solve it in R and its numerical solution.
Availability
Please see Omniascience website for details, and the repository containing the code used in the book.
Also available through UPCommons in this direction.
Sallan, Jose M.; Lordan, Oriol; Fernandez, Vicenc (2015). Modeling and Solving Linear Programming with R. Omniascience.
Abstract
Linear programming is one of the most extensively used techniques in the toolbox of quantitative methods of optimization. One of the reasons of the popularity of linear programming is that it allows to model a large variety of situations with a simple framework. Furthermore, a linear program is relatively easy to solve. The simplex method allows to solve most linear programs efficiently, and the Karmarkar interior-point method allows a more efficient solving of some kinds of linear programming. The power of linear programming is greatly enhanced when came the opportunity of solving integer and mixed integer linear programming. In these models all or some of the decision variables are integers, respectively.
In this book we provide a brief introduction to linear programming, together with a set of exercises that introduce some applications of linear programming. We will also provide an introduction to solve linear programming in R. For each problem a possible solution through linear programming is introduced, together with the code to solve it in R and its numerical solution.
Availability
Please see Omniascience website for details, and the repository containing the code used in the book.
Also available through UPCommons in this direction.
martes, 24 de marzo de 2015
viernes, 27 de febrero de 2015
An Examination of the Effects of Self-Regulatory Focus on the Perception of the Media Richness: The Case of E-Mail
Citation
Armengol, Xavier; Fernandez, V.; Simo, P.; Sallan, J. M. (2015). An Examination of the Effects of Self-Regulatory Focus on the Perception of the Media Richness: The Case of E-Mail. International Journal of Business Communication
http://dx.doi.org/10.1177/2329488415572780
Abstract
Communication is a key element in organizations’ business success. The media richness theory and the channel expansion theory are two of the most influential theories regarding the selection and use of communication media in organizations; however, literature has focused little on the effects of self-regulation by managers and employees in these theories. To analyze these topics, this study develops an empirical investigation by gathering data from 600 managers and employees using a questionnaire. The results suggest that the perception of media richness is positively affected when the individual shows a promotion focus or strategy.
Armengol, Xavier; Fernandez, V.; Simo, P.; Sallan, J. M. (2015). An Examination of the Effects of Self-Regulatory Focus on the Perception of the Media Richness: The Case of E-Mail. International Journal of Business Communication
http://dx.doi.org/10.1177/2329488415572780
Abstract
Communication is a key element in organizations’ business success. The media richness theory and the channel expansion theory are two of the most influential theories regarding the selection and use of communication media in organizations; however, literature has focused little on the effects of self-regulation by managers and employees in these theories. To analyze these topics, this study develops an empirical investigation by gathering data from 600 managers and employees using a questionnaire. The results suggest that the perception of media richness is positively affected when the individual shows a promotion focus or strategy.
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