Comparison of SCImago journal rank indicator with journal impact factor

[Loet Leydesdorff]

Dear Johan, 
 
You state in this paper that "(t)he rankings listed in Table 7 are limited
to the 5 highest ranked journals out of nearly 8,500." Would it be possible
to bring the 47 metrics for these nearly 8,500 journals online (e.g., as an
excel file)? Or can you send it? I might, for example, be interested in
three (rotated) factors in the case of your data while you provide two
(unrotated) prinicipal compontents. 
 
As expected, you found in this paper a clear distinction along the two
principal components between usage-based and citation-based indicators. Let
me recall the following figure from my paper "
<http://www.leydesdorff.net/jcr04> Visualization of the Citation Impact
Environments of Scientific Journals: An online mapping exercise," (JASIST
58(1) (2007) 25-38), at p. 28:
 



Figure 1: Component plot in rotated space (sources: JCR, 1993; Bensman,
2001; forthcoming; Bensman & Wilder, 1998).

 
This figure is very similar to the one which I circulated yesterday evening,
and based on Bensman's analysis of usage data in 1993 combined with JCR data
for that same year. In my opinion, the model is the same as underlying your
recent paper. 
 
On the first component ("size"), I found high loadings for both Bensman's
indicators "Indiana University Chemistry Library" usage data and "Faculty
Score". Interestingly, the values of the eigenvectors are almost similar to
the ones which I found last night using 2006 data, notably: 59% for the size
factor and 23% for the c/p factor (impact, etc.) against 25% last night.
Extraction of a third factor (9.7%) separates the size-factor into two
factors representing usage and size. 

(Figure based on 1993 data!; Source: Bensman, 2001, etc.)
 
Thus, I would expect a three-factor solution to be more interesting than the
extraction of two principal components.
 
Would you mind to make your data public? I mean the table of 8,500 journals
versus 47 metrics.
 
With best wishes, 
 
 
Loet

________________________________

Loet Leydesdorff
Amsterdam School of Communications Research (ASCoR),
Kloveniersburgwal 48, 1012 CX Amsterdam.
Tel.: +31-20- 525 6598; fax: +31-20- 525 3681
loet at leydesdorff.net ; http://www.leydesdorff.net/



> -----Original Message-----
> From: ASIS&T Special Interest Group on Metrics
> [mailto:SIGMETRICS at LISTSERV.UTK.EDU] On Behalf Of Johan Bollen
> Sent: Thursday, April 24, 2008 5:51 AM
> To: SIGMETRICS at LISTSERV.UTK.EDU
> Subject: Re: [SIGMETRICS] Comparison of SCImago journal rank
> indicator with journal impact factor
>
> Adminstrative info for SIGMETRICS (for example unsubscribe):
> http://web.utk.edu/~gwhitney/sigmetrics.html
>
> Hi Loet,
>
> with respect to your previous email, we performed a PCA on
> about 50 metrics (so far excluding the h-index and SJR) for
> the MESUR project (<http://www.mesur.org/>). It may be of
> interest to the readers of this list (see attached graphic)
> and is discussed in this paper:
>
> Bollen, J., Van de Sompel, H. and Rodriguez, M. A. Towards
> Usage- based Impact Metrics: First Results from the MESUR
> Project. In Proceedings of the Joint Conference on Digital
> Libraries, Pittsburgh, PA, June 16-20, 2008.
> <http://arxiv.org/abs/0804.3791>
>
> The metrics in the graph carry code names that can be resolved here:
> <http://www.mesur.org/Metrics.html>
>
> Regards,
>
> Johan.
>
>
> 

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