2017-10-24 software

TurtleGraphics v1.0-7

A bugfix release of the TurtleGraphics package for R is now available for download from CRAN.


Today I have been awarded a habilitation degree, thesis title: New algorithms for data aggregation and analysis: construction, properties, and applications.

Research Visit @ Deakin University

From July 17 until August 8, 2017 I shall be visiting Dr Simon James, Prof. Gleb Beliakov, Dr Tim Wilkin and their colleagues at the School of Information Technology, Deakin University in Burwood, Victoria, Australia. The support by the SEBE Researcher in Residence 2017 Program from Deakin University is fully acknowledged.
2017-07-06 new paper

Measuring Traffic Congestion

Measuring traffic congestion: An approach based on learning weighted inequality, spread and aggregation indices from comparison data has been accepted for publication in Applied Soft Computing. Assigned DOI is 10.1016/j.asoc.2017.07.014. Simon James did a wonderful work leading this research project. The paper was written in collaboration with researchers from Deakin University, namely: Gleb Beliakov, Shannon Pace, Nicola Pastorello, Elodie Thilliez, and Rajesh Vasa.
Abstract. As cities increase in size, governments and councils face the problem of designing infrastructure and approaches to traffic management that alleviate congestion. The problem of objectively measuring congestion involves taking into account not only the volume of traffic moving throughout a network, but also the inequality or spread of this traffic over major and minor intersections. For modelling such data, we investigate the use of weighted congestion indices based on various aggregation and spread functions. We formulate the weight learning problem for comparison data and use real traffic data obtained from a medium-sized Australian city to evaluate their usefulness.
2017-06-21 invited talk

Invited Tutorial @ AGOP 2017

Today I gave a tutorial at the 9th International Summer School on Aggregation Operators – AGOP 2017 held at University of Skövde, Sweden.

Abstract. Aggregation theory classically deals with functions to summarize a sequence of numeric values, e.g., in the unit interval. Since the notion of componentwise monotonicity plays a key role in many situations, there is an increasingly growing interest in methods that act on diverse ordered structures.

However, as far as the definition of a mean or an averaging function is concerned, the internality (or at least idempotence) property seems to be of a relatively higher importance than the monotonicity condition. In particular, the Bajraktarević means or the mode are among some well-known non-monotone means.

The concept of a penalty-based function was first investigated by Yager in 1993. In such a framework, we are interested in minimizing the amount of "disagreement" between the inputs and the output being computed; the corresponding aggregation functions are at least idempotent and express many existing means in an intuitive and attractive way.

In this talk I focus on the notion of penalty-based aggregation of sequences of points in Rd, this time for some d≥1. I review three noteworthy subclasses of penalty functions: componentwise extensions of unidimensional ones, those constructed upon pairwise distances between observations, and those defined by measuring the so-called data depth. Then, I discuss their formal properties, which are particularly useful from the perspective of data analysis, e.g., different possible generalizations of internality or equivariances to various geometric transforms. I also point out the difficulties with extending some notions that are key in classical aggregation theory, like the monotonicity property.

2017-05-23 new paper

EUSFLAT'17: Fitting symmetric fuzzy measures for discrete Sugeno integration

A paper by Simon James and I entitled Fitting symmetric fuzzy measures for discrete Sugeno integration has been accepted for publication in the Proceedings of EUSFLAT conference.
2017-04-20 invited workshop

rOpenSci Text Workshop

This week I'm at the rOpenSci Text Workshop organized by Ken Benoit from the London School of Economics and Political Science. This workshop is designed to bring the R text package developers' community, to share experiences and knowledge, and hopefully foster cooperation.
2017-04-07 software

stringi 1.1.5 released

Another bugfix release of the stringi package for R is on its way to CRAN. The package provides powerful string processing facilities to R users and developers and is ranked as one of the most often downloaded R extensions.


* [GENERAL] `stringi` now requires ICU4C >= 52.

* [GENERAL] `stringi` now requires R >= 2.14.

* [BUGFIX] Fixed errors pointed out by `clang-UBSAN` in `stri_brkiter.h`.

* [BUILD TIME] #238, #220: Try "standard" ICU4C build flags if a call
to `pkg-config` fails.

* [BUILD TIME] #258: Use `CXX11` instead of `CXX1X` on R >= 3.4.

* [BUILD TIME, BUGFIX] #254: `dir.exists()` is R >= 3.2.