



EDITORIAL 

Year : 2018  Volume
: 26
 Issue : 3  Page : 8788 

HIndex and the other metrics in analyzing Authors' impact
Cenk Demirdover
EditorinChief, Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey
Date of Web Publication  2Jul2018 
Correspondence Address: Cenk Demirdover Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, Faculty of Medicine, Dokuz Eylul University, Izmir Turkey
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/13006878.235783
How to cite this article: CenkD. HIndex and the other metrics in analyzing Authors' impact
. Turk J Plast Surg 2018;26:878 
Dear Colleagues,
The increase in the number of scientific articles brought up the problem of evaluating authors' metrics. The number of publications, the number of citations to the publications, and impact factors of the journals are the most commonly used parameters. However, extracting and validating these data are extremely important in obtaining objective results.
Hindex
The hindex was first introduced in 2005 by Hirsch to calculate an author's scientific research achievement. ^{[1]} It is based on the number of an author's individual publications and the number of citations that these publications have attracted. Because it is very easy to understand and calculate the hindex, it gained popularity among various scientific tools, such as Web of Science, Scopus, and Google Scholar. It is defined as h and equals the number of publications that have received at least h citations. For example, an author's hindex is 8, if he/she has at least 8 publications that each has received at least 8 citations. The correlation between citations and the number of publications is shown in [Figure 1].  Figure 1: The correlation between citations and the number of publications
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In order to understand the calculation of hindex, examples of hindex for different authors are given in [Table 1].  Table 1: The calculation of hindices for three different authors, each having 11 publications with different number of citations
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The number of total citations of Author C's publications is 147, which is much lower than Author's B's citations. But still, Author C has a higher hindex, compare to Author B. Author B is mostly concentrated on the first 4 publications, and the rest of his/her publications have attracted much less citations. On the other hand, Author C had more consistent citations for his/her publications. The hindex of Author A will raise to 9, as soon as he receives the 9 ^{th} citation for his publication 9.
Due to these disadvantages of the hindex, more author evaluation metrics have been proposed. Bornmann et al. published a metaanalysis of hindex and its variants. ^{[2]} All these variants seek better objective outputs; however, their additional parametric inputs lose their simplicity. The Hirschtype indices, such as gindex, h(2)index, aindex, rindex, arindex, m quotient, mindex, hwindex, hmindex basically reflect either the productivity of an author or the impact of a publication. ^{[1],[2]} Some of the other metrics for author impacts have been discussed below.
Gindex
In 2006, a year after hindex has been defined, Egghe proposed the gindex giving additional credits for the highly cited articles. Given a set of articles ranked in decreasing order of the number of citations that they received, the gindex is the (unique) largest number such that the top g articles received on average at least g citations. ^{[3]}
Ageweighted citation rate
The number of citations for a publication is divided by the year since it has been published. New and less cited publications that have no contribution to the hindex increase ageweighted citation rate (AWCR). ^{[4]}
Ageweighted index
The AWindex is defined as the square root of the AWCR to allow comparison with the hindex; it approximates the hindex if the (average) citation rate remains more or less constant over the years. ^{[4]}
The Eigenfactor score
The Eigenfactor score has been developed as an academic research project of Bergstrom et al., in 2008. It is correlated with the journal impact factor. Citations in a high impact factor journals get more credits than the journals with lower impact factor. ^{[5]}
Eindex
The eindex takes into account the highly cited articles of an author which is ignored in hindex. It helps to discriminate the authors with the same hindex. ^{[6]}
Windex
If w of an author's publications has at least 10 w citations each and the other publications have fewer than 10 (w+1) citations, his/her windex is w. This also implies that one has not achieved the higher level: w+1 of his/her papers have at least 10 (w+1) citations each. ^{[7]}
Author impact factor
Author impact factor (AIF), which is similar to the journal impact factor. The AIF of an Author A in year t is the average number of citations given by papers published in year t to papers published by A in a period of Δt years before year t. AIF is correlated with the scientific productivity of an author for a certain period. ^{[8]}
The most common components of these indices are the number of publications, the number of citations, average number of citations per paper, average number of citations per author, average number of papers per author, the age of the publication, and journal impact factors. Since every index uses a different combination of these components, author citation metrics may differ significantly. To choose the best index, one should consider the basic fact that lies beneath in determining these indices.
References   
1.  Hirsch JE. An index to quantify an individual's scientific research output. Proc Natl Acad Sci U S A 2005;102:1656972. [ PUBMED] 
2.  Bornmann L, Mutz R, Hug SE, Daniel HD. A multilevel metaanalysis of studies reporting correlations between the h index and 37 different h index variants. J Informetr 2011;5:34659. 
3.  Egghe L. Theory and practise of the gindex. Scientometrics 2006,69:13152. 
4.  Harzing A. The Publish or Perish Book [electronic resource]: Your Guide to Effective and Responsible Citation Analysis. 1 ^{st} ed. Melbourne, Australia: Tarma Software Research Pty., Ltd.; 2010. p. 21032. 
5.  Bergstrom CT, West JD, Wiseman MA. The eigenfactor metrics. J Neurosci 2008;28:114334. [ PUBMED] 
6.  Zhang CT. The eindex, complementing the hindex for excess citations. PLoS One 2009;4:e5429. [ PUBMED] 
7.  Wu Q. The windex: A measure to assess scientific impact by focusing on widely cited papers. J Assoc Infor Sci Techn 2010;61:60914. 
8.  Pan RK, Fortunato S. Author impact factor: Tracking the dynamics of individual scientific impact. Sci Rep 2014;4:4880. [ PUBMED] 
[Figure 1]
[Table 1]
