Department of Gastrointestinal Hepatobiliary, Jiali Chi-Mei Hospital.
Department of Medical Research, Chi-Mei Medical Center.
Medicine (Baltimore). 2021 Mar 12;100(10):e25016. doi: 10.1097/MD.0000000000025016.
The h-index of a researcher refers to the maximum number h of his/her publications that has at least h citations via the concept of the square area. The x-index is determined by the maximum area of a rectangle under the curve to interpret authors' individual research achievements (IRAs). However, the properties of both metrics have not been compared and discussed before. This study aimed to investigate whether both metrics of h- and x-index are suitable for evaluating IRAs in a short period of years.
By searching the PubMed database (Pubmed.com), we used the keyword "PLoS One" (journal) and downloaded 50,000 articles published in 2015 and 2016. A total of 146,346 citations were listed in PubMed Central and 27,035 authors(with h-index ≥1) were divided into 3 parts. Correlation coefficients among metrics (ie, AIF, h, g, Ag, and x-index) were examined. The bootstrapping method used for estimating 95% confidence intervals was applied to compare differences in metrics among author groups. The most cited authors and topic burst were visualized by social network analysis. The most prominent countries/areas were highlighted by the x-index and displayed via choropleth maps.
Results demonstrated that, first, the h-index had the least relation to other metrics and failed to differentiate authors' IRAs among groups, particularly in a short time period. Second, the top 3 highest x-index for countries were the United States, China, and the UK but with the productivity-oriented feature. Third, the most cited medical subject headings (ie, MeSH terms) were genome, metabolome, and microbiology, and the most cited author was Lori Newman (whose x-index = 13.52, and h = 2) from Switzerland with the article (PMID = 26646541) cited 291 times. The need for the x-index combined with a visual map for displaying authors' IRAs was verified and recommended.
We verified that the h-index failed to differentiate authors' IRAs among author groups in a short time period. The x-index combined with the Kano map is recommended in research for a better understanding of the authors' IRAs in other journals or disciplines, not just limited to the journal of PloS One as we did in this study.
研究人员的 h 指数是指其出版物的最大数量 h，这些出版物通过平方面积的概念至少有 h 次引用。x 指数是通过曲线下矩形的最大面积来确定的，用于解释作者的个人研究成果（IRA）。然而，这两个指标的性质以前没有进行过比较和讨论。本研究旨在探讨 h 指数和 x 指数这两个指标是否适合在短时间内评估 IRA。
通过在 PubMed 数据库（Pubmed.com）中搜索“PLoS One”（期刊），我们下载了 2015 年和 2016 年发表的 50,000 篇文章。PubMed Central 列出了总计 146,346 次引用，27,035 位 h 指数≥1 的作者被分为 3 部分。检验了指标之间的相关系数（即 AIF、h、g、Ag 和 x 指数）。应用 bootstrap 方法估计 95%置信区间，以比较作者组之间指标的差异。通过社会网络分析可视化最受引用的作者和主题爆发。通过 choropleth 地图突出显示 x 指数最高的国家/地区。
结果表明，首先，h 指数与其他指标的相关性最小，无法区分作者在组间的 IRA，尤其是在短时间内。其次，国家的前 3 个最高 x 指数是美国、中国和英国，但具有以生产力为导向的特征。第三，最受引用的医学主题词（即 MeSH 术语）是基因组、代谢组和微生物学，最受引用的作者是来自瑞士的 Lori Newman（x 指数=13.52，h=2），他的文章（PMID=26646541）被引用 291 次。验证并推荐了使用 x 指数和可视化地图来显示作者 IRA 的需求。
我们验证了 h 指数在短时间内无法区分作者在作者组之间的 IRA。建议在研究中使用 x 指数与 Kano 图相结合，以便更好地了解作者在其他期刊或学科中的 IRA，而不仅仅限于我们在本研究中使用的 PLoS One 期刊。
