2019-03-25 new paper

**An inherent difficulty in the aggregation of multidimensional data**

Accepted for publication in
*IEEE Transactions on Fuzzy Systems*
— *An inherent difficulty in the aggregation of multidimensional data*
by Raúl Pérez-Fernández, Bernard De Baets, and me. Abstract below.

Abstract.In the field of information fusion, the problem of data aggregation has been formalized as an order-preserving process that builds upon the property of monotonicity. However, fields such as computational statistics, data analysis and geometry, usually emphasize the role of equivariances to various geometrical transformations in aggregation processes. Admittedly, if we consider a unidimensional data fusion task, both requirements are often compatible with each other. Nevertheless, in this paper we show that, in the multidimensional setting, the only idempotent functions that are monotone and orthogonal equivariant are the over-simplistic weighted centroids. Even more, this result still holds after replacing monotonicity and orthogonal equivariance by the weaker property of orthomonotonicity. This implies that the aforementioned approaches to the aggregation of multidimensional data are irreconcilable, and that, if a weighted centroid is to be avoided, we must choose between monotonicity and a desirable behaviour with regard to orthogonal transformations.

2019-03-13 new paper

**Should we introduce a dislike button for academic papers?**

The abstract of our (by Agnieszka Geras, Grzegorz Siudem, and me)
recent paper to be published
in *Journal of the Association for Information Science and Technology*
can be found below.

Abstract.On the grounds of the revealed, mutual resemblance between the behaviour of users of Stack Exchange and the dynamics of the citations accumulation process in the scientific community, we tackled an outwardly intractable problem of assessing the impact of introducing "negative" citations.

Although the most frequent reason to cite a paper is to highlight the connection between the two publications, researchers sometimes mention an earlier work to cast a negative light. While computing citation-based scores, for instance the h-index, information about the reason why a paper was mentioned is neglected. Therefore it can be questioned whether these indices describe scientific achievements accurately.

In this contribution we shed insight into the problem of "negative" citations, analysing data from Stack Exchange and, to draw more universal conclusions, we derive an approximation of citations scores. Here we show that the quantified influence of introducing negative citations is of lesser importance and that they could be used as an indicator of where attention of scientific community is allocated.

2019-03-12 software

**R package stringi 1.4.3 released**

This month's new release of the R package

`stringi`

brings significant improvements in the way substring extraction tasks
are performed.
Change-log since v1.3.1:

* [NEW FEATURE] #30: New function `stri_sub_all()` - a version of `stri_sub()` accepting list `from`/`to`/`length` arguments for extracting multiple substrings from each string in a character vector. * [NEW FEATURE] #30: New function `stri_sub_all<-()` (and its `%<%`-friendly version, `stri_sub_replace_all()`) - for replacing multiple substrings with corresponding replacement strings. * [NEW FEATURE] In `stri_sub_replace()`, `value` parameter has a new alias, `replacement`. * [NEW FEATURE] New convenience functions based on `stri_remove_empty()`: `stri_omit_empty_na()`, `stri_remove_empty_na()`, `stri_omit_empty()`, and also `stri_remove_na()`, `stri_omit_na()`. * [BUGFIX] #343: `stri_trans_char()` did not yield correct results for overlapping pattern and replacement strings. * [WARNFIX] #205: `configure.ac` is now included in the source bundle.

2019-03-08 software

A long out-standing release of the R package

`agop`

is now available on CRAN. See below for more details.
Change-log:

0.2-2 /2019-03-05/ * [IMPORTANT CHANGE] All functions dealing with binary relations now are named like `rel_*`. Moreover, `de_transitive()` has been renamed `rel_reduction_hasse()`. * [IMPORTANT CHANGE] The definition of `owa()`, `owmax()`, and `owmin()` is now consistent with that of (Grabisch et al., 2009), i.e., uses nondecreasing vectors, and not nonincreasing ones. * [NEW FUNCTIONS] `rel_closure_reflexive()`, `rel_reduction_reflexive()`, `rel_is_symmetric()`, `rel_closure_symmetric()`, `rel_is_irreflexive()`, `rel_is_asymmetric()`, `rel_is_antisymmetric()`, `rel_is_cyclic()`, etc., modify given adjacency matrices representing binary relations over finite sets. * [NEW FUNCTIONS] some predefined fuzzy logic connectives have been added, e.g. ,`tnorm_minimum()`, `tnorm_drastic()`, `tnorm_product()`, `tnorm_lukasiewicz()`, `tnorm_fodor()`, `tconorm_minimum()`, `tconorm_drastic()`, `tconorm_product()`, `tconorm_lukasiewicz()`, `tconorm_fodor()`, `fnegation_classic()`, `fnegation_minimal()`, `fnegation_maximal()`, `fnegation_yager()`, `fimplication_minimal()`, `fimplication_maximal()`, `fimplication_kleene()`, `fimplication_lukasiewicz()`, `fimplication_reichenbach()`, `fimplication_fodor()`, `fimplication_goguen()`, `fimplication_goedel()`, `fimplication_rescher()`, `fimplication_weber()`, `fimplication_yager()`. * [NEW FUNCTION] `check_comonotonicity()` determines if two vectors are comonotonic. * [NEW FUNCTIONS] `pord_spread()`, `pord_spreadsym()`, `pord_nd()` - example preorders on sets of vectors. * [NEW FEATURE] `plot_producer()` gained a new argument: `a`. * [BUGFIX] `rel_closure_transitive()` - a resulting matrix was not necessarily transitive. * [BUGFIX] `prepare_arg_numeric_sorted` (internal, C++) did not sort some vectors. * [BUGFIX] All built-in aggregation functions now throw an error on empty vectors. * [INFO] The package no longer depends on the `Matrix` package. The `igraph` package is only suggested. * [INFO] Most of the functions are now implemented in C++.

2019-03-01 new paper

**Penalty-based data aggregation in real normed vector spaces**

To be published in the Proceedings of the
AGOP'19 conference:
joint work with Lucian Coroianu entitled
*Penalty-based data aggregation in real normed vector spaces*.
Abstract below.

Abstract.The problem of penalty-based data aggregation in generic real normed vector spaces is studied. Some existence and uniqueness results are indicated. Moreover, various properties of the aggregation functions are considered.

2019-02-14 software

**R package stringi 1.3.1 released**

A new major release of the R package

`stringi`

(one of
the most often downloaded extensions on CRAN)
is available.
Check out the change-log for more information.
Change-log:

* [BACKWARD INCOMPATIBILITY] #335: A fix to #314 (by design) prevented the use of the system ICU if the library had been compiled with `U_CHARSET_IS_UTF8=1`. However, this is the default setting in `libicu`>=61. From now on, in such cases the system ICU is used more eagerly, but `stri_enc_set()` issues a warning stating that the default (UTF-8) encoding cannot be changed. * [NEW FEATURE] #232: All `stri_detect_*` functions now have the `max_count` argument that allows for, e.g., stopping at first pattern occurrence. * [NEW FEATURE] #338: `stri_sub_replace()` is now an alias for `stri_sub<-()` which makes it much more easily pipable (@yutannihilation, @BastienFR). * [NEW FEATURE] #334: Added missing `icudt61b.dat` to support big-endian platforms (thanks to Dimitri John Ledkov @xnox). * [BUGFIX] #296: Out-of-the box build used to fail on CentOS 6, upgraded `./configure` to `--disable-cxx11` more eagerly at an early stage. * [BUGFIX] #341: Fixed possible buffer overflows when calling `strncpy()` from within ICU 61. * [BUGFIX] #325: Made `./configure` more portable so that it works under `/bin/dash` now. * [BUGFIX] #319: Fixed overflow in `stri_rand_shuffle()`. * [BUGFIX] #337: Empty search patters in search functions (e.g., `stri_split_regex()` and `stri_count_fixed()`) used to raise too many warnings on empty search patters.

2019-02-14 new paper

**Piecewise linear approximation of fuzzy numbers: algorithms, arithmetic operations and stability of characteristics**

A paper by me, Lucian Coroianu and Przemyslaw Grzegorzewski
entitled
*Piecewise linear approximation of fuzzy numbers: algorithms, arithmetic operations and stability of characteristics*,
has been accepted for publication
in *Soft Computing*.

Abstract.The problem of the piecewise linear approximation of fuzzy numbers giving outputs nearest to the inputs with respect to the Euclidean metric is discussed. The results given in Coroianu et al. (Fuzzy Sets Syst 233:26–51, 2013) for the 1-knot fuzzy numbers are generalized for arbitrary n-knot (n>=2) piecewise linear fuzzy numbers. Some results on the existence and properties of the approximation operator are proved. Then, the stability of some fuzzy number characteristics under approximation as the number of knots tends to infinity is considered. Finally, a simulation study concerning the computer implementations of arithmetic operations on fuzzy numbers is provided. Suggested concepts are illustrated by examples and algorithms ready for the practical use. This way, we throw a bridge between theory and applications as the latter ones are so desired in real-world problems.

2019-01-16 new paper

**Supervised Learning to Aggregate Data with the Sugeno Integral**

Abstract.The problem of learning symmetric capacities (or fuzzy measures) from data is investigated toward applications in data analysis and prediction as well as decision making. Theoretical results regarding the solution minimizing the mean absolute error are exploited to develop an exact branch-refine-and-bound-type algorithm for fitting Sugeno integrals (weighted lattice polynomial functions, max-min operators) with respect to symmetric capacities. The proposed method turns out to be particularly suitable for acting on ordinal data. In addition to providing a model that can be used for the general data regression task, the results can be used, among others, to calibrate generalized h-indices to bibliometric data.