Mapping patent classifications: portfolio and statistical analysis, and the comparison of strengths and weaknesses
Mapping patent classifications: portfolio and statistical analysis, and the comparison of strengths and weaknesses
Loet Leydesdorff 0 1 2
Dieter Franz Kogler 0 1 2
Bowen Yan 0 1 2
Bowen Yan 0 1 2
0 SUTD-MIT International Design Centre, Singapore University of Technology and Design , Singapore 487372 , Singapore
1 School of Architecture, Planning and Environmental Policy, UCD Centre for Spatial Dynamics, University College Dublin , Richview Campus, Belfield, Dublin 4 D04 V1W8 , Ireland
2 Amsterdam School of Communication Research (ASCoR), University of Amsterdam , PO Box 15793, 1001 NG Amsterdam , The Netherlands
The Cooperative Patent Classifications (CPC) recently developed cooperatively by the European and US Patent Offices provide a new basis for mapping patents and portfolio analysis. CPC replaces International Patent Classifications (IPC) of the World Intellectual Property Organization. In this study, we update our routines previously based on IPC for CPC and use the occasion for rethinking various parameter choices. The new maps are significantly different from the previous ones, although this may not always be obvious on visual inspection. We provide nested maps online and a routine for generating portfolio overlays on the maps; a new tool is provided for ''difference maps'' between patent portfolios of organizations or firms. This is illustrated by comparing the portfolios of patents granted to two competing firms-Novartis and MSD-in 2016. Furthermore, the data is organized for the purpose of statistical analysis.
Patent data provide a primary data source for scholars interested in the development of
(e.g., Strumsky et al. 2012)
. In a comprehensive study of US
Jaffe and Trajtenberg (2002)
, for example, argued that patents and patent
citations provide ‘‘a window on the knowledge economy.’’ However, patents are indicators
of inventions and not innovations
(Archibugi and Pianta 1992; Pavitt 1985; Griliches
. Like publication data, patent data provide a wealth of information about knowledge
(Hunt et al. 2007)
, references to prior art, forward citation, inventor and applicant
addresses, and classifications. Note that patenting can also be strategic or defensive given a
firm’s technical expertise and product portfolio
(Alkemade et al. 2015)
Different from journal articles, patents are not refereed among peers, but by examiners
at the patent office, among other things, on the criterion of whether the submitted
application provides novelty. The purpose of the novelty requirement is to prevent prior art from
being patented again. The examiner is entitled to add references to prior art,1 but most
importantly organizes the patent in a patent classification system. In the absence of an
equivalent for journals, the classification system can be considered as the intellectual
organization of the database of novel products and processes of economic value.
was the first who proposed to use co-classifications of patents for
characterizing the technological positions of firms with the objective of quantifying
technological opportunities and research spillovers. For this purpose, each patent can be
represented as a vector of classifications.
used the cosine between these
vectors as a similarity measure
(Salton and McGill 1983)
. Sets of patents (e.g., patent
portfolios of firms) can be modeled as aggregates of these vectors into matrices. The
resulting matrix can be used for statistical analysis and/or the visualization of the
similarities as projections on a map
(Schiffman et al. 1981; Waltman et al. 2010)
In a series of studies, we developed instruments for the mapping and analysis of patent
data with a focus mainly on data of the US Patent and Trade Office (USPTO). US patenting
is considered the most competitive and is therefore most relevant to technology and
(Granstrand 1999; Jaffe 1989; Jaffe and Trajtenberg 2002; Lee 2013)
USPTO maintains a freely available database of patent data at http://patft.uspto.gov/
netahtml/PTO/search-adv.htm. This database is copied at other places, such as Google
Patents, the National Bureau of Economic Research (NBER) in the USA, and PatentsView
(http://www.patentsview.com). PatentsView adds to the data by providing disambiguated
inventor and assignee identifiers (Monath and McCallum 2015).
Building on approaches suggested in previous studies
(e.g., Breschi et al. 2003; Leten
et al. 2007; Verspagen 1997)
, we developed instruments for the mapping and analysis of
patent data using International Patent Classifications (IPC). IPC was developed by the
World International Property Organization (WIPO) and further elaborated by the European
Patent Office (EPO) into the European Classification System ECLA. This classification
uses up to fourteen characters for the indexing. As of 1 January 2013, however, USPTO
and EPO use the new Cooperative Patent Classifications (CPC) which build on ECLA. In
addition to the various patent offices of the EU member states, China, Korea, Russia, and
Mexico, among others, are in the process of aligning their classifications with CPC. In this
study, we use CPC for the mapping, review and integrate the results and routines from the
1 At EPO all references are added by the examiner.
previous studies, revise some of the methodological choices, and update the routines and
Choices of parameters
In addition to the choice of a similarity criterion such as the cosine, a number of parameter
choices are relevant for the mapping of patent data: the choice of domains in terms of
patent offices (USPTO, EPO, WIPO, etc.), the classification system (CPC, IPC, etc.), the
clustering algorithm (e.g., co-classification, co-citation, bibliographic coupling), etc. The
classifications can be used with different levels of detail by using more digits of the
respective classes, i.e. main- and/or sub-classes.
Kogler et al. (2017b) used IPC at the four-digit level for portfolio analysis;
Yan and Luo
used IPC at the three-digit level (IPC-3).
Leydesdorff et al. (2014)
used both three
and four digits of IPC for exploring a dynamic approach. With similar objectives, Kay
et al. (2014) composed 466 IPC categories at different levels of depth after preprocessing
their data from the comprehensive PATSTAT database.2
Schoen et al. (2012)
database of the Corporate Invention Board (CIB) for the construction of their own
(Alkemade et al. 2015)
. Archibugi and Pianta (1992) combined IPC with the
Standard Industrial Classification (SIC) using a concordance table. However, the objective
of these last authors was not to provide a map or overlays.
In this study, we use CPC at the four digit level. CPC is similar to IPC in the first four
digits, but the classification of individual patents can be changed in the process of
reclassification; new classes have also been added. Furthermore, CPC contains new
categories classified under ‘‘Y’’ that span different sections of CPC in order to indicate new
technological developments such as nanotechnology and technologies for the mitigation of
(Scheu et al. 2006; Veefkind et al. 2012)
. Currently, there are nine of these
Y-classes. Since these boundary-spanning classes are back-tracked into the database, they
introduce new links between previously unrelated classes. As a result, one can expect
changes in the networks among the classes. All values in this study are based on CPC at the
4-digit level (CPC-4) instead of IPC-4.
Co-classification is a binary measure at the level of individual patents. Co-citation of
classes or bibliographic couplings among them can be considered as more refined measures
of the strength of the relationships.
Yan and Luo (2017)
compared twelve techniques for
the mapping of patent data in terms of citation relations, inventive activities, etc., among
121 IPC classes at the 3-digit level. The conclusion was that maps based on
Jaccardnormalized bibliographic coupling at the (disaggregated) patent level—‘‘A1’’ in the
classification of methods provided by these authors—significantly outperformed maps
based on the cosine values among of aggregated citations among IPC classes
et al. 2014, 2015)
. Actually, Yan and Luo (2017, at p. 435) conclude that ‘‘class-to-class
cosine similarity among aggregated citations (A2) performed the worst in various analyses,
although it is popularly used for constructing network maps of patents.’’ This critique
prompted us to reconsider on previous choices of parameters.
In this study, we combine our two approaches: we use bibliographic coupling among
CPC-4 classes at the level of patents as individual documents. We first construct the
asymmetrical (2-mode) matrix of patents (cited) in the rows versus citing patents
2 Further information regarding access to PATSTAT can be found at:
aggregated into the 654 CPC classes at the 4-digit level in the columns. The Jaccard index
and cosine values are then computed over the 654 columns
(Leydesdorff and Vaughan
. The resulting (1-mode) matrices can be utilized as input into the mapping exercise.
For the clustering and subsequent coloring of the resulting map we use a methodology
recently developed by
Leydesdorff et al. (2017)
for journal mapping. VOSviewer (v1.6.5;
28 September 2016) provides both a community-finding algorithm and visualization
(Waltman et al. 2010)
. We use this algorithm for generating a hierarchically decomposed
set of maps of patent classes. Although the resulting maps are statistical and cannot claim
semantic authority, they can serve the heuristics by offering a baseline. Both the
Jaccardbased map and the cosine-based one were decomposed into clusters using these statistics.
VOSviewer enables us to visualize 654 data points without cluttering the labels on the
screen by foregrounding and backgrounding strong and weak presences, respectively. The
CPC classes are fractionally counted so that each patent contributes with a value of one.
We harvested patent data from 1976 to July of 2016 from USPTO and PatentsView3 on
January 11, 2017. The data set contains 5,175,268 utility patents. Each patent is classified
in one or more CPC classes. The definitions of CPC classes are available among other
places at https://www.uspto.gov/web/patents/classification/cpc.html. As noted, CPC and
IPC are identical in terms of the first four digits. However, IPC contains 630 four-digit
classes, whereas CPC distinguishes 705 such classes, of which 654 are currently in use. We
use these 654 classes.
The 5M? patents cite 7,203,533 patents. First, we constructed a 2-mode matrix of the 654
classes—aggregates of the 5M? citing patents—versus the 7M? cited patents. This
matrix was then used for computing the symmetrical 1-mode matrices of 654 * 654
Jaccard and cosine values, respectively. Equations (1) and (2) provide the formulas for
calculating Jaccard and cosine similarity between two random variables.
Jaccard ¼ Pin¼1 xi2 þ
Cosine ¼ pffiPffiffiffiffiffinffiPffiffiffiffiffiinffi¼ffi2ffi1pxiffiPyffiffiiffiffiffinffiffiffiffiffiffiffiffiffi
i¼1 xi i¼1 yi2
The Jaccard matrix is based on counting the cited patents as binary [A1 in
Yan and Luo
],4 whereas numerical values can be used for computing cosine values: a patent can
be cited more than once in a CPC-class of citing patents.
Yan and Luo (2017)
this cosine based on values at the individual patent level as a third option A3 and conclude
3 Patentsview is available at http://www.patentsview.org/.
4 A non-binary equivalent of the Jaccard index is provided by the Tanimoto index
(Lipkus 1999; cf. Salton
and McGill 1983, at pp. 203f)
that ‘‘in some cases of our analysis, A3 is no worse than A1.’’ However, the QAP (Pearson)
correlation between the resulting two matrices—diagonals excluded—is 0.786
(p \ .0001). Thus, one can also expect the two maps to be different. We explore and
compare both maps.
The cosine can be considered as a proximity measure in the vector space and
(1 - cosine) thus provides a distance measure. While the corresponding ‘‘Jaccard
distance’’ (=1 - Jaccard) is widely accepted in the literature as well, we note that the Jaccard
index in contrast is a relational measure. From the perspective of graph theory, the
geodesic would be a better measure for the distance between two nodes in a network
et al. 2011)
. As a distance measure, in our opinion, one should therefore preferably use
(1 - cosine) and not the Jaccard distance.
Both the Jaccard and the cosine matrices were decomposed using the routine decomp.exe
(available at http://www.leydesdorff.net/jcr15/program.htm). The maps based on the
Jaccard indices are available (i) at http://www.leydesdorff.net/cpcmaps for each class
(bottom-up) and (ii) at http://www.leydesdorff.net/cpcmaps/scope using hierarchical clustering
top-down. One has the option either to access the various maps directly in the.jpg format or
to webstart a map using VOSviewer. The latter option provides an analyst with follow-up
options such as choosing other parameters or exporting the files in formats used by other
Jaccard and cosine values generated on the basis of the 2-mode matrix of patents versus
classes can be very small since these matrices are sparse. During the decomposition, for
example, VOSviewer saves files with fewer decimals than the cosine values so that these
values are rounded to zero. This inflates the modularity and generates small clusters. In
order to avoid this effect, we multiplied all values by 1000. For the global map, this makes
no difference in the case of cosine values and hardly any difference for a map based on
Jaccard values; but the larger values improve the decomposition because the additional
zeros otherwise increase the number of small clusters. However, the larger values can no
longer be used for the distance measurement because they can be larger than one. For this
reason, we use the cosine between aggregated citations among classes as the proximity
measure in the routines about portfolio management. (This file ‘‘cos_cpc.dbf’’ is available at
http://www.leydesdorff.net/cpc_cos/cos_cpc.dbf; see the ‘‘Appendix’’ section for details.)
We provide a routine (CPC.exe; see the ‘‘Appendix’’ section) for generating overlays on
the new map. Overlays on maps can be used for portfolio management by science-policy
makers and R&D management
(Kogler et al. 2017b; Leydesdorff et al. 2016; Rotolo et al.
. We add to the portfolio mapping, the option of a ‘‘difference map’’ so that one can
visually compare two portfolios in a single map, indicated with two different colors.
5 For the convenience of the user, the symmetrical Jaccard matrix is made available at http://www.
leydesdorff.net/cpcmaps/jaccard-sym.csv. Analogously, the cosine-based maps and decompositions are
brought online at http://www.leydesdorff.net/cpc_cos and http://www.leydesdorff.net/cpc_cos/scope,
respectively. The symmetrical cosine matrix is available at http://www.leydesdorff.net/cpcmaps/cosine-sym.
Using the routine (made available at http://www.leydesdorff.net/cpc_cos/portfolio/
index.htm; see the ‘‘Appendix’’ section for instructions), one can first retrieve a specific
patent set using any search string valid in the USPTO search interface. The routine then
generates a file vos.txt that can be read by VOSviewer and generate overlays.6 In order to
facilitate comparisons among sets a column variable is added to a file matrix.dbf for each
run. This file can be read into programs such as SPSS for statistical analysis. Similar, a row
variable is added to the file rao.dbf containing the value of Rao-Stirling diversity D
1982; Stirling 2007)
and Zhang et al.’s (2016) improved measure 2D3 [= 1/(1 – D)] for the
sample under study. In our opinion, these diversity measures can be considered as
measures of ‘‘related variety’’
(Frenken et al. 2007)
, since the disparity is measured in addition
to the variety
(Rafols and Meyer 2010)
. The variety is ecologically related in terms of the
disparity among the categories. If the files matrix.dbf and rao.dbf are not already present or
were deleted, they are generated de novo.
The routine CPC.exe first asks for a name of the sample (e.g., ‘‘Boston’’) that is used to
label the column and row variables added. The routine is technically similar to the one
defined in Kogler et al. (2017b) for IPC classes, but based on the improved map using
CPC-4. The routine CPC2.exe asks for two sets of downloaded patents in order to generate
a difference map. Difference maps can be used for comparing portfolios of different units
Jaccard or cosine-based maps?
The global maps based on the Jaccard index (Fig. 1) and the cosine (Fig. 2) are obviously
dissimilar. Whereas we are able to provide the cosine-based map with an interpretation, we
find this difficult for the Jaccard-based one. A lexigraphical approach did not work for
making a choice, since the headers of CPC classes are dominated by words such as
‘‘material,’’ ‘‘device,’’ etc. Table 1, for example, shows the ten most frequently used words
in the six clusters distinguished in the Jaccard-based matrix (using VOSviewer), whereas
Table 2 provides the equivalent information for the nine clusters distinguished in the
cosine-based matrix. Neither table is semantically rich.
Reading Fig. 2 clockwise, one first encounters at the top right (between 12 and two
o’clock) a cluster about energy, including labels about technologies for ‘‘mitigation of
climate change’’ and ‘‘reduction of greenhouse gases.’’ Following the clock, one observes a
pink cluster (between 3 and 4 o’clock) with a focus on organic chemistry and enzymes.
This cluster is followed (between 5 and 6 o’clock) by a cluster in green with titles referring
to macromolecules and paint. Below that a cluster (in light-brown) refers to furniture, etc.
To the left (at 9 o’clock), we see a cluster in yellow with titles referring to communication.
At 11 o’clock, a cluster follows (in orange) with a focus on electrical engineering. A
relatively small cluster (in brown, at 10 o’clock) between the latter two focuses on light. A
cluster colored light-blue is organized along the second diagonal; we would characterize it
as ‘‘materials and devices.’’ The labels ‘‘material’’ and ‘‘device’’ are italicized in Table 2;
they provide the backbone of the map.
6 VOSviewer is freely available at http://www.vosviewer.com
(Van Eck and Waltman 2010; Waltman et al.
One can compare classifications using Crame`r’s V as a measure of Chi square between
zero and one (Table 3). Neither the Jaccard-based clustering in six groups nor the
cosinebased in nine groups is statistically independent of the organization of CPC into the nine
main classes A to H, and Y (p \ .001 in both cases).
Table 3 confirms that the two maps are considerably different. However, both are even
more different from the CPC-4 classification than from each other. In sum, we will use the
cosine-based map (Fig. 2) as the basemap for portfolio management. Using CPC.exe,
samples downloaded from the USPTO database will be overlaid on this map, similar to the
Kogler et al. (2013)
where this was performed for U.S. metropolitan areas.
Kogler et al. (2017b) used the portfolios granted to inventors in the twenty cities in 2014,
but based on IPC-4. We reproduce their results here using issue dates in 2016, CPC classes,
and the new map. The objective is to learn more about the operational difference between
using IPC-4 and CPC-4: in which respects do the classification schemes make a difference?
In Table 4, the cities are listed with the number of patents retrieved in both 2014 and 2016.
The data for these 20 cities in 2014 and 2016 are rank-correlated with q = .98 (p \ .01). In
other words, the retrieval is not incidental.
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Table 5 provides the diversity values for these 20 cities. The number of patents is not
correlated to the diversity scores: the Pearson correlation between N and D is 0.16 (and
0.12 between N and 2D3; n.s.). Metropolitan cities such as Paris and Boston have the
highest scores, whereas patents from Wageningen—the home town of the single
agricultural university in the Netherlands—are specific. The results, however, can also be
counterintuitive and thus raise further questions for follow-up research. Rotterdam, for example,
scores third on diversity behind Paris and Boston. One can envisage a systematic study of
diversity in global or so-called ‘‘smart cities,’’ etc., as a perspective for future research.
The values are different from the ones based on IPC-4 in 2014: Shanghai, for example,
which was ranked in the first position in 2014 based on IPC, is now rated in 9th position
once CPC serves as the underlying classification system. The change from IPC to CPC thus
makes a difference in this evaluation; the rank-ordering differs significantly between 2014
and 2016 (q = .42; n.s.).
Using city names, one should be aware that some cities can be more administratively
circumscribed than others. For the USA, a classification in terms of metropolitan areas is
available. The Core-based Statistical Area (CBSA)7 of Boston, for example, can be
searched in USPTO using the following string: ‘‘(ic/(Essex OR Middlesex OR Norfolk OR
Plymouth OR Suffolk OR Boston OR Cambridge) AND IS/MA) OR (ic/(Quincy OR
Rockingham OR Strafford) AND IS/NH) AND ISD/2016$$.’’ The retrieval is 2521 as
against 2265 in 2014. However, since there is no CBSA equivalent for the other countries,
we abstained in this study from this further elaboration
(Grossetti et al. 2014; Maisonobe
et al. 2016)
7 A Core Based Statistical Area (CBSA) is a U.S. geographic area defined by the Office of Management and
Budget (OMB) that consists of one or more counties (or equivalents) anchored by an urban center of at least
10,000 people plus adjacent counties that are socioeconomically tied to the urban center by commuting.
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A matrix like the one of (20) cities versus (654) CPC-4 classes can be used for various
forms of statistical analysis. For example, one can use discriminant analysis given the
grouping of cities in countries. Nineteen of the twenty profiles are correctly identified by
nation using the CPC classes; the exception is Beersheva, which is predicted as belonging
to the French group. However, the prediction is considerably improved compared to the
one based on IPC, when only 17 or the 20 (85%) were correctly predicted.
Using the cosine values of CPC vectors among the 20 cities, one can generate a local
map among the cities differently from the overlay on the global map for each of them
(Fig. 4). VOSviewer distinguishes three groups. Table 6 shows the three-factor solution of
the matrix. (Factor analysis is based on the Pearson correlations. Unlike the cosine, the
Pearson correlation normalizes to the mean.)
This three-factor solution explains 69.79% of the variance. This solution is only weakly
related to the corresponding three-factor matrix made on the basis of 2014 data and IPC
(r = .31; p B .05). Major cities are grouped as factor 1; factor 2 is related to this first
factor by Chinese cities (Beijing, Shanghai, and Nanjing), which share a pattern also with
technologically oriented cities such as Grenoble, Toulouse, and Eindhoven. Factor 3 is set
apart with other factor loadings of three Dutch cities (Amsterdam, Rotterdam, and
Wageningen) and Dalian in China. Why the grouping is in some respects different between
Fig. 4 and Table 6 require further analysis beyond the scope of this study.
Visual comparisons between two portfolios
The routine CPC2.exe (available at http://www.leydesdorff.net/cpc_cos/portfolio) allows
for the further extension of comparing two portfolios with each other in a single map. (For
instructions see the ‘‘Appendix’’ section or at http://www.leydesdorff.net/cpc_cos/
Applying the same procedure as above for cities, but now using firm names the retrieval
was 276 patents granted at USPTO in 2016 using, for example, the search string ‘‘(an/
Novartis or aanm/Novartis) and isd/2016$$.’’ ‘‘AN’’ and ‘‘AANM’’ are fields code for the
names of assignees and applicants, respectively, in the advanced search engine of USPTO.
Note that the applicant is not always the assignee of a patent; the applicant may also be the
inventor, whereas the assignee is the owner of the patent.
In Fig. 5, the resulting map is compared with a similar one using the 350 patents granted
to MSD in 2016. The routine CPC2.exe provides a file vos2.txt that can be used as input to
VOSviewer (and corresponding files for Pajek). The red-colored nodes on this map
indicate the CPC-4 classes in which Novartis has more patents than MSD, and the
greencolored ones the classes with more patents of MSD than Novartis. Novartis, for example,
has a more pronounced portfolio in the region in the figure labeled ‘‘filters implantable into
blood;’’ the portfolio of MSD is stronger in the area indicated around ‘‘semiconductor
Discussion and concluding remarks
Indicators for measuring the distance or relatedness between distinct sets of technological
knowledge categories are of interest in a number of disciplines; for example, management
(Almeida 1996; Makri et al. 2010)
(Jaffe 1986; Teece et al. 1994)
(Fischer et al. 2006; Quatraro 2010; Boschma et al. 2015)
. The strength of
the relationships between unique sets of technological expertise can inform us about the
level of specialization and coherence amongst firms, regions, and/or countries. This in turn
has been linked to the level of productivity of these units
(Nesta and Saviotti 2005; Kogler
et al. 2013)
, and can also serve as an indicator for potential diversification and innovation
opportunities as well as limitations
(Colombelli et al. 2014; Feldman et al. 2015; Kogler
et al. 2017a)
One of our objectives has been to show how sensitive the maps and overlays are to
choices of parameters. The maps are not natural, like geographic maps, but remain
constructs that originate from discursive reasoning. Consequently, one cannot infer on the
basis of visual inspection that one representation is better than another; but one needs
analytical arguments for the choices. For this reason, it was urgent to take
Yan and Luo’s
critique seriously and redo the maps. As we have shown, the results based on CPC-4
are roughly similar, but different in important respects from IPC-based maps. In our
opinion, the ostensable similarity is to a large extent due to the use of similar methods; the
empirical results are in important respects significantly different.
We did not follow Yan and Luo’s preference for the Jaccard index, but used the cosine.
The Jaccard index is relational and binary, whereas the cosine is a numerical and a
(Burt 1982; Leydesdorff 2014)
. Portfolios projected on a global map
can be considered as positions. We suggested to study relations using a local map and
provided a tool for this purpose.
The global maps were not interpretable when using the Jaccard index (Fig. 1), but they
were interpretable on the basis of the cosine (Fig. 2). However, we agree on using the basic
(2-mode) matrix of cited patents versus citing aggregates into CPC classes. Using this
disaggregated level can be considered as an important improvement on previous maps. The
input data is more finely-grained by orders of magnitude.
The multi-variate analysis confirmed the improvement. The prediction based on
discriminant analysis was improved from 85 to 95%. The (varimax) rotation of the
eigenvectors provided us with additional and meaningful insights in the comparisons among
cities. The positions of the major Chinese cities among cities in the global domain (factor
1) and cities with strong engineering (factor 2) are suggested in the cosine-based map.
Visualization is a strong instrument because maps can be provided with an
interpretation more easily than numerical statistics. However, the latter are needed in the
background for making analytical arguments. A direct comparison between two units (e.g.,
competing firms) using a map, however, can provide a first orientation to their differences
in terms of strengths and weaknesses.
Acknowledgements We are grateful to Jordan Comins and two anonymous referees for comments on a
previous draft. BY acknowledges support by the Academic Research Fund Tier 2 of the Singapore Ministry
of Education. DK acknowledges funding by the European Research Council, Grant no. 715631.
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution,
and reproduction in any medium, provided you give appropriate credit to the original author(s) and the
source, provide a link to the Creative Commons license, and indicate if changes were made.
Preparing input files
Download the following files from http://www.leydesdorff.net/cpc_cos/
portfolio (or https://leydesdorff.github.io/cpc/portfolio) into a single folder on
your hard disk:
cpc.dbf (with basic information about the classes);
uspto1.exe (needed for the downloading of USPTO patents);
cos_cpc.dbf (needed for the computation of distances on the map);
Options within cpc.exe
The incremental construction of the files matrix.dbf and rao.dbf
The program asks for a short name (B10 characters) in each run. This name will
be used as the variable label in later parts of the routine;
The first option is to download the patents from USPTO at http://patft.uspto.
gov/netahtml/PTO/search-adv.htm; detailed instructions for the downloading
can be found at http://www.leydesdorff.net/ipcmaps;
USPTO has a maximum of 1000 records at a time, but one is allowed to
followup batches; after the download is completed, save the files in another folder or
as a zip file;
After each run, a column variable is added to the (local) file matrix.dbf
containing the distribution of the 654 CPC classes in the document set under
study. If the file matrix.dbf is absent, it is generated de novo and the current run
is considered as generating the first variable; matrix.dbf can be read by Excel,
SPSS, etc., for further (statistical) analysis;
Output files in each run
Similarly, a row variable is added after each run to the file rao.dbf containing
diversity measures (explained in the article) as variables. This file is also
generated de novo if previously absent. Distances are based on [1 - cos(x,y)]
for each two distributions x and y of aggregated citation at the level of CPC-4
The routine cpc2cos.exe reads the file matrix.dbf and produces cosine.net and
coocc.dat as (normalized) co-occurrence matrices that can be used in network
analysis and visualization programs such as Pajek or UCInet.
The file ‘‘vos.txt’’ can be read by VOSviewer for mapping the portfolio under
study at the four-digit level of CPC; the distances and colors (corresponding to
clusters) in the maps are based on the base-map provided in Fig. 2 above;
The files cpc.vec and cpc.cls can be used as a vector and cluster files in the
Pajek file provided at http://www.leydesdorff.net/cpc_cos/. This allows for
layouts other than VOSviewer and for more detailed network analysis and
statistics. The file cpc.cls is a so-called cluster file which can be used in Pajek,
among other things, for the extraction of partitions.
The various fields in the USPTO records are organized in a series of databases
that can be related (e.g., in MS Access) using the field ‘‘nr.’’
Visual comparison among portfolios (using cpc2.exe)
One can compare two portfolios (as in Fig. 5 above) using cpc2.exe (available at
One first runs cpc.exe for the one set (e.g., city1);
Replace the downloaded patents (p1.htm, p2.htm, etc.) with the set for the
second unit (e.g., city2) and run cpc2.exe;
The file vos2.txt generated is an input file to VOSviewer. The red-colored nodes
indicate the CPC-4 classes in which the first unit is stronger than the second; the
green-colored nodes indicate the relative strength of the second set;
The files cpc2.vec and cpc2.cls provide the corresponding input files for Pajek.
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