Science mapping on-line; beta-version

Loet Leydesdorff loet at LEYDESDORFF.NET
Tue Nov 2 02:48:43 EST 2004

** apologies for cross-postings

Dear colleagues,

Maps of aggregated citation relations among journals can be based on a
variety of multi-variate techniques. For various reasons, the vector-space
model (based on the cosine) has become selected as the least problematic
option in the literature. At  <>  I have now brought online the
cosine-matrices for the 5714 journals which are processed from the citing
side in the most recent Journal Citation Report of the Science Citation
Index 2003. The files are organized in such a way that one can directly
import them into Pajek, a freeware program for the visualization which is
made by our colleagues of the Mathematics Department of the University of
Ljubljana. Pajek can be downloaded at
<>  or by clicking from my page.

Each of the journals is listed as a separate entry. By clicking on the
journal name one obtains an ASCII file which contains the information about
the journal's environment in the data-definition language which Pajek can
read. There are some instructions on how one can produce a map of the
journals with this tool. It should work quite easily. The advantage of this
method above bringing the pictures on-line is, on the one side, that the
user can now colour journals differently, resize labels, etc., as one would
like it best. Using the cosine matrices, on the other side, protects ISI's
copyrights on the original data because one is not able to reconstruct
citation data from these (normalized) cosine values.

The details of the parameters and the procedures are provided in the
introductory text on the webpage. If one needs further clarification,
please, feel free to contact me or to make suggestions so that I can improve
this text also for the other users. Please, consider this as a beta-version.

With kind regards,



Loet Leydesdorff
Amsterdam School of Communications Research (ASCoR)
Kloveniersburgwal 48, 1012 CX Amsterdam
Tel.: +31-20- 525 6598; fax: +31-20- 525 3681
 <mailto:loet at> loet at ;

 <> The Challenge of
Scientometrics ;  <> The
Self-Organization of the Knowledge-Based Society

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