
EGGHE, Leo
We give mathematical explanations of some empirical results obtained by Campanario in Scientometrics 99(2):289298, (2014).

Egghe, Leo
This paper introduces a new method for information retrieval of documents that are represented by a vector. The novelty of the algorithm lies in the fact that no (generalized) pnorms are used as a matching function between the query and the document (as is done e.g. by Salton and others) but a function that measures the relative dispersion of the terms between a document and a query. This function originates from an earlier paper of the author where a good measure of relative concentration was introduced, used in informetrics to measure the degree of specialization of a journal w.r.t. the...


EGGHE, Leo
In this note we show that the multiplier k that appears in the law of Bradford is not the average production of
articles per author nor the average number p of articles
per journal, contradicting some earlier statements of
Goffman and Warren and of Yablonsky. We remark however
that the Bradford multiplier might be close to p in
a lot of cases, being merely a coincidence of the special
functional relation between ~1 and k which we develop
in full detail. We finally show that K = kplA (p = number
of Bradford groups, A = total numbers of articles) is a
universal constant for the bibliography. Furthermore, K
is...

EGGHE, Leo
Informetric systems are formalized in order to make them
suitable for mathematical dual analysis: the duality of sources vs. items (sources being the objects that produce while the items are the objects that are produced). The special place of empirical laws, such as those of Bradford, Leimkuhler. Mandelbrot and Lotka, in this framework is indicated. The paper closes with a section on some of the fundamental problems in informetric systems: higher dimensions, time dependence and fractal aspects.

EGGHE, Leo
In a previous article (L. Egghe, JASIS 37(4); p. 246255,
1966) we further developed the theory of Bradford???s law
by deriving a theoretical formula for the Bradford multiplier and for the number of items, produced by the most productive source in every Bradford group. In this article we apply these results to some classical bibliographies, for which we determine the underlying law of Leimkuhler and also different Bradford groupings. We
also extend the above mentioned theory in order to be ap
plicable to incomplete bibliographies (s.a. citation tables or bibliographies truncated before the Groos droop). Finally this extension also has an application in determining...

EGGHE, Leo

EGGHE, Leo
It is shown that a normalized version of the gindex is a good normalized impact and concentration measure. A proposal for such a measure by Bartolucci is improved.

EGGHE, Leo
The Sshaped functional relation between the mean citation score and the proportion of top 10% publications for the 500 Leiden Ranking universities is explained using results of the shifted Lotka function. Also the concave or convex relation between the proportion of top 100??% publications, for different fractions ??, is explained using the obtained new informetric model.

EGGHE, Leo
We show mathematically that the successindex can be any of the following impact indices, dependent on the value of the threshold used in the definition of the successindex: Hirschindex (hindex), gindex, generalized Wu and Kosmulskiindices, the average.

EGGHE, Leo; ROUSSEAU, Ronald
This article has been inspired by the activity index and problems in its proper understanding. It studies a basic relative contribution index which is placed in the context of countries??? publication contributions. Two versions are proposed: one being an average of ratios (AoR) and the other one a ratio of averages (RoA). A LotkaianZipfian framework is used to model the two versions of the proposed indicator. A remarkable difference between the two approaches (RoA vs. AoR) is found when determining the fraction of units (countries) that have a value larger than one. This observation contributes to the understanding of the...

EGGHE, Leo

EGGHE, Leo; ROUSSEAU, Ronald
One of the major drawbacks of the classical Lotka function is that arguments only start from the value 1. However, in many applications one may want to start from the value 0, e.g. when including zero received citations. In this article we consider the shifted Lotka function, which includes the case of zero items. Basic results for the total number of sources, the total number of items and the average number of items per source are given in this framework. Next we give the rankfrequency function (Zipftype function) corresponding to the shifted Lotka function and prove their exact relation. The...

EGGHE, Leo
A new explanation, using exponential functions, is given for the Sshaped functional relation between the mean
citation score and the proportion of top 10% (and other percentages) publications for the 500 Leiden Ranking
universities.
With this new model we again obtain an explanation for the concave or convex relation between the proportion
of top 100??% publications, for different fractions of ??.

EGGHE, Leo
The relative hindex, proposed by L.A.S. Dias, is not useful to compare the scientific performance of researchers. This is shown by examples. More adequate alternatives include the gindex and the Rindex.

EGGHE, Leo

EGGHE, Leo
The minimum configuration to have a hindex equal to h is h papers each having h citations, hence h(2) citations in total. To increase the hindex to h + 1 we minimally need (h + 1)(2) citations, an increment of I1(h) = 2h + 1. The latter number increases with 2 per unit increase of h. This increment of the second order is denoted I2(h) =2. If we define I1 and I2 for a general Hirsch configuration (say n papers each having f(n) citations) we calculate I1(f) and I2(f) similarly as for the hindex. We characterize all functions f for...

EGGHE, Leo; ROUSSEAU, Ronald
Based on earlier results about the shifted Lotka function, we prove an implicit functional relation between the Hirsch index (hindex) and the total number of sources (T). It is shown that the corresponding function, h(T), is concavely increasing. Next, we construct an implicit relation between the hindex and the impact factor IF (an average number of items per source). The corresponding function h(IF) is increasing and we show that if the parameter C in the numerator of the shifted Lotka function is high, then the relation between the hindex and the impact factor is almost linear.

Egghe, L.
We present a study of four impact measures: the hindex, the gindex, the Rindex and the jindex. The gindex satisfies the transfer principle, the jindex satisfies the opposite transfer principle while the h and Rindices do not satisfy any of these principles. We study general inequalities between these measures and also determine their maximal and minimal values, given a fixed total number of citations.

Goovaerts, Marc; Leinders, Dirk
In this paper, we evaluate the quality of the metadata of an OAIcompliant repository based on the completeness metric proposed by X. Ochoa and E. Duval. This study focuses on the completeness of the metadata records as defined by M.A. Sicilia et al, where machineunderstandability is a mandatory requirement for completeness. The goal is to use the completeness metric as a tool for harvesters and repository managers to evaluate easily the quality of the metadata of a repository. We focus on the metadata used by the communities of agriculture, aquaculture and environment from the VOA3R project. The OceanDocs repository serves...