Evolutionary Biological Data Science Laboratory

trend h-index

The trend h-index (Sidiropoulos et al. 2007) is essentially the opposite of the contemporary h-index. It is designed to measure how current an author's impact is by how recently they are being cited. The trend score for a publication is measured as

$$S^t_i = \gamma \sum\limits_{j=1}^{C_i}{\left(Y-Y_{j.i}+1\right)^{-\delta}}$$

where γ and δ are parameters (often set to 4 and 1, respectively, just as with the contemporary h-index) and Y_j.i is the year of the j^th citation for publication i. If the number of citations for publication i in year Y_k is C_i.k, this can also be written as $$S^t_i = \gamma \sum\limits_{k=1}^{Y}{C_{i.k}\left(Y-Y_k+1\right)^{-\delta}}.$$The trend h-index is the largest value for which an author has h^t publications with at least S^t ≥ h^t.

$$h^t = \underset{i}{\max}\left(i \leq S^t_i\right)$$

Example

Publications are ordered by adjusted number of citations, from highest to lowest.

Citations (Ci)	59	26	16	11	11	10	3	4	2	1	1	1	3	0	0	0	0	0
—1997—	1	0	—	—	0	0	—	—	—	—	—	—	1	0	—	—	—	—
—1998—	6	3	3	—	1	0	—	—	—	—	—	—	1	0	0	—	—	—
—1999—	12	10	2	—	1	2	—	1	—	—	—	—	0	0	0	—	—	—
—2000—	13	4	6	4	5	6	0	2	0	0	—	—	1	0	0	0	—	—
—2001—	27	9	5	7	4	2	3	1	2	1	1	1	0	0	0	0	0	0
Adjusted Citations (\(S^{t}_i\))	156.80	60.33	37.67	36.00	28.33	22.67	12.00	9.33	8.00	4.00	4.00	4.00	3.80	0.00	0.00	0.00	0.00	0.00
Rank (i)	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
								hC = 8

The largest rank where \(i \leq S^{t}_i\) is 8.

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