News
June 21, 2015
This is a new major version of igraph, and then why not call
it 1.0.0. This does not mean that it is ready, it'll never be
ready.
The biggest changes in the release are
 the new function names. Most functions were renamed to
make them more consistent and readable. (Relax, old names
can still be used, no need to update any code.)
 Better operations for vertex and edge sequences. Most functions
return proper vertex/edge sequences instead of numeric ids.
 The versatile
make_()
and make_graph()
functions to
create graphs.
 Many functions were renamed. Old names are not documented,
but can still be used.
 A generic
make_graph()
function to create graphs.
 A generic
layout_()
(not the underscore!) function
to create graph layouts, see also add_layout_()
.
 The igraph data type has changed. You need to call
upgrade_graph()
on graphs created with previous igraph
versions.
 Vertex and edge sequence operations: union, intersection, etc.
 Vertex and edge sequences can only be used with the graphs they
belong to. This is now strictly checked.
 Most functions that return a (sub)set of vertices
or edges return vertex or edge sequences instead.
 Vertex and edge sequences have a
[[
operator now,
for easy viewing of vertex/edge metadata.
 Vertex and edge sequences are implemented as weak references.
See also the
as_ids()
function to convert them to simple ids.
 Vertex order can be specified for the circle layout now.
 DavidsonHarel layout algorithm
layout_with_dh()
.
 GEM layout algorithm
layout_with_gem()
.
 Neighborhood functions have a
mindist
parameter for the
smallest distance to consider.
all_simple_paths()
function to list all simple paths in a graph.
triangles()
lists all triangles in a graph.
 FruchtermanReingold and KamadaKawai layout algorithms
rewritten from scratch. They are much faster and follow the
original publications closely.
 Nicer printing of graphs, vertex and edge sequences.
local_scan()
function calculates scan statistics.
 Embeddings:
embed_adjacency_matrix()
and embed_laplacian_matrix()
.
 Product operator:
*
, the same graph multiple times. Can be also
used as rep()
.
 Better default colors, color palettes for vertices.
 Random walk on a graph:
random_walk()
adjacenct_vertices()
and incident_edges()
functions,
they are vectorized, as opposed to neighhors()
and incident()
.
 Convert a graph to a long data frame with
as_long_data_frame()
.
Too many to list. Please try if your issue was fixed and (re)report
it if not. Thanks!
April 21, 2014
Some bug fixes, to make sure that the code included in
'Statistical Analysis of Network Data with R' works. See
https://github.com/kolaczyk/sand
 Graph drawing: fix labels of curved edges, issue #181.
 Graph drawing: allow fixing edge labels at given positions,
issue #181.
 Drop the 'type' vertex attribute after bipartite projection,
the projections are not bipartite any more, issue #255.
 Print logical attributes in header properly (i.e. encoded by
l
,
not x
, which is for complex attributes. Issue #578.
 Add a constructor for
communities
objects, see create.communities()
.
Issue #547.
 Better error handling in the GraphML parser.
 GraphML reader is a bit more lenient now; makes it possible to read
GraphML files saved from yWorks apps.
 Fixed a bug in
constaint()
, issue #580.
 Bipartite projection now detects invalid edges instead of giving
a cryptic error, issue #543.
 Fixed the
simplify
argument of graph.formula()
, which was
broken, issue #586.
 The function
crossing()
adds better names to the result,
fixes issue #587.
 The
sir()
function gives an error if the input graph is
not simple, fixes issue #582.
 Calling igraph functions from igraph callbacks is not allowed now,
fixes issue #571.
February 4, 2014
There are a bunch of new features in the library itself, and
other important changes in the life of the project. Thanks everyone
for sending code and reporting bugs!
igraph's development has moved from Launchpad to github.
This has actually happened several month ago, but never
announced officially. The place for reporting bugs is
at https://github.com/igraph/igraph/issues.
igraph's homepage is now hosted at http://igraph.org, and it is
brand new. We wanted to make it easier to use and modern.
You can download nightly builds from igraph at
http://igraph.org/nightly. Source and binary R packages (for windows
and OSX), are all built.
 Added a demo for hierarchical random graphs, invoke it via
demo(hrg)
.
 Make attribute prefixes optional when writing a GraphML file.
 Added function
mod.matrix()
.
 Support edge weights in leading eigenvector community detection.
 Added the LAD library for checking (sub)graph isomorphism, version 1.
 Logical attributes.
 Added
layout.bipartite()
function, a simple twocolumn layout
for bipartite graphs.
 Support incidence matrices in bipartite Pajek files.
 Pajek files in matrix format are now directed by default, unless they
are bipartite.
 Support weighted (and signed) networks in Pajek when file is in
matrix format.
 Fixed a bug in
barabasi.game()
, algorithm psumtreemultiple
just froze.
 Function
layout.mds()
by default returns a layout matrix now.
 Added support for Boolean attributes in the GraphML and GML readers
and writer.
 Change MDS layout coordinates, first dim is according to first
eigenvalue, etc.
plot.communities()
(plot.igraph()
, really) draws a border
around the marked groups by default.
 printing graphs now converts the
name
graph attribute to character
 Convenience functions to query and set all attributes at once:
vertex.attriubutes()
, graph.attributes()
and edge.attributes()
.
 Function
graph.disjoint.union()
handles attributes now.
 Rewrite
graph.union()
to handle attributes properly.
rewire()
: now supports the generation and destruction of loops.
 ErdosRenyi type bipartite random graphs:
bipartite.random.game()
.
 Support the new options (predecessors and inbound_edges) of
get_shortest_paths()
, reorganized the output of
get.shortest.paths()
completely.
 Added
graphlets()
and related functions.
 Fix modularity values of multilevel community if there are no merges
at all.
 Fixed bug when deleting edges with FALSE in the matrix notation.
 Fix
bonpow()
and alpha.centrality()
and make sure that the
sparse solver is called.
tkplot()
news: enable setting coordinates from the command line
via tkplot.setcoords()
and access to the canvas via
tkplot.canvas()
.
 Fixed a potential crash in
igraph_edge_connectivity()
, because of an
uninitialized variable in the C code.
 Avoiding overflow in
closeness()
and related functions.
 Check for NAs after converting 'type' to logical in
bipartite.projection()
.
graphNEL
conversion functions only load the 'graph' package if it was
not loaded before and they load it at the end of the search path,
to minimize conflicts.
 Fixed a bug when creating graphs from adjacency matrices, we now convert
them to double, in case they are integers.
 Fixed an invalid memory read (and a potential crash) in the infomap
community detection.
 Fixed a memory leak in the functions with attribute combinations.
 Removed some memory leaks from the SCG functions.
 Fixed some memory leaks in the ray tracer.
 Fixed memory leak in
graph.bfs()
and graph.dfs()
.
 Fix a bug in triad census that set the first element of the result
to NaN.
 Fixed a crash in
is.chordal()
.
 Fixed a bug in weighted mudularity calculation, sum of the weights
was truncated to an integer.
 Fixed a bug in weighted multilevel communtiies, the maximum weight
was rounded to an integer.
 Fixed a bug in
centralization.closeness.tmax()
.
 Reimplement pushrelabel maximum flow with gap heuristics.
 Maximum flow functions now return some statistics about the push
relabel algorithm steps.
 Function
arpack()
now gives error message if unknown options are
given.
 Fixed missing whitespace in Pajek writer when the ID attribute was
numeric.
 Fixed a bug that caused the GML reader to crash when the ID
attribute was nonnumeric.
 Fixed issue #500, potential segfault if the two graphs in BLISS
differ in the number of vertices or edges.
 Added
igraphtest()
function.
 Fix dyad census instability, sometimes incorrect results were
reported.
 Dyad census detects integer overflow now and gives a warning.
 Function
add.edges()
does not allow now zeros in the vertex set.
 Added a function to count the number of adjacent triangles:
adjacenct.triangles()
.
 Added
graph.eigen()
function, eigenproblems on adjacency matrices.
 Added some workarounds for functions that create a lot of
graphs,
decompose.graph()
and graph.neighborhood()
use it.
Fixes issue #508.
 Added weights support for
optimal.community()
, closes #511.
 Faster maximal clique finding.
 Added a function to count maximum cliques.
 Set operations: union, intersection, disjoint, union, difference,
compose now work based on vertex names (if they are present) and
keep attributes, closes #20.
 Removed functions
graph.intersection.by.name()
,
graph.union.by.name()
, graph.difference.by.name()
.
 The
+
operator on graphs now calls graph.union()
if both
argument graphs are named, and calls graph.disjoint.union()
otherwise.
 Added function
igraph.version()
.
 Generate graphs from a stochastic block model:
sbm.game()
.
 Do not suggest the stats, XML, jpeg and png packages any more.
 Fixed a
set.vertex/edge.attribute
bug that changed both
graph objects, after copying (#533)
 Fixed a bug in
barabasi.game
that caused crashes.
 We use PRPACK to calculate PageRank scores
see https://github.com/dgleich/prpack
 Added
'which
argument to bipartite.projection
(#307).
 Add
normalized
argument to closeness functions, fixes issue #3.
 R: better handling of complex attributes,
[[
on vertex/edge sets,
fixes #231.
 Implement the
start
argument in hrg.fit
(#225).
 Set root vertex in ReingoldTilford layout, solves #473.
 Fix betweenness normalization for directed graphs.
 Fixed a bug in
graph.density
that resulted in incorrect values for
undirected graphs with loops
 Fixed a bug when many graphs were created in one C call
(e.g. by
graph.decompose
), causing #550.
 Fixed sparse
graph.adjacency
bugs for graphs with one edge,
and graphs with zero edges.
 Fixed a bug that made BellmanFord shortest paths calculations fail.
 Fixed a
graph.adjacency
bug for undirected, weighted graphs and
sparse matrices.
main
, sub
, xlab
and ylab
are proper graphics parameters
now (#555).
graph.data.frame
coerces arguments to data frame (#557).
 Fixed a minimum cut bug for weighted undirected graphs (#564).
 Functions for simulating epidemics (SIR model) on networks,
see the
sir
function.
 Fixed argument ordering in
graph.mincut
and related functions.
 Avoid copying attributes in query functions and print (#573),
these functions are much faster now for graphs with many
vertices/edges and attributes.
 Speed up writing GML and GraphML files, if some attributes are
integer. It was reallyreally slow.
 Fix multiple root vertices in
graph.bfs
(#575).
Released Oct 28, 2013
Some bugs fixed:
 Fixed a potential crash in the infomap.community() function.
 Various fixed for the operators that work on vertex names (#136).
 Fixed an example in the arpack() manual page.
 arpack() now gives error message if unknown options
are supplied (#492).
 Better arpack() error messages.
 Fixed missing whitespace in Pajek writer when ID attribute
was numeric.
 Fixed dyad census instability, sometimes incorrect
results were reported (#496).
 Fixed a bug that caused the GML reader to crash when the ID
attribute was nonnumeric
 Fixed a potential segfault if the two graphs in BLISS
differ in the number of vertices or edges (#500).
 Added the igraphtest() function to run tests from R (#485).
 Dyad census detects integer overflow now and gives a warning (#497).
 R: add.edges() does not allow now zeros in the vertex set (#503).
 Add C++ namespace to the files that didn't have one.
Fixes some incompatibility with other packages (e.g. rgl)
and mysterious crashes (#523).
 Fixed a bug that caused a side effect in set.vertex.attributes(),
set.edge.attributes() and set.graph.attributes() (#533).
 Fixed a bug in degree.distribution() and cluster.distribution()
(#257).
Released May 16, 2013
Worked two CRAN check problems, and a gfortran bug (string bound
checking does not work if code is called from C and without string
length arguments at the "right" place).
Otherwise identical to 0.6.51.
Released February 27, 2013
Fixing an annoying bug, that broke two other packages on CRAN:
 Setting graph attributes failed sometimes, if the attributes were
lists or other complex objects.
Released February 24, 2013
This is a minor release, to fix some very annoying bugs in 0.6.4:
 igraph should now work well with older R versions.
 Eliminate gap between vertex and edge when plotting an edge without an arrow.
Fixes #1118448.
 Fixed an outofbounds array indexing error in the DrL layout, that
potentially caused crashes.
 Fixed a crash in weighted betweenness calculation.
 Plotting: fixed a bug that caused misplaced arrows at rectangle
vertex shapes.
Released February 2, 2013
The version number is not a mistake, we jump to 0.6.4 from 0.6,
for technical reasons. This version was actually never really
released, but some R packages of this version were uplodaded to
CRAN, so we include this version in this NEW file.

Added a vertex shape API for defining new vertex shapes, and also
a couple of new vertex shapes.

Added the get.data.frame() function, opposite of graph.data.frame().

Added bipartite support to the Pajek reader and writer, closes bug
#1042298.

degree.sequence.game() has a new method now: "simple_no_multiple".

Added the is.degree.sequence() and is.graphical.degree.sequence()
functions.

rewire() has a new method: "loops", that can create loop edges.

Walktrap community detection now handles isolates.

layout.mds() returns a layout matrix now.

layout.mds() uses LAPACK instead of ARPACK.

Handle the '~' character in write.graph and read.graph. Bug
#1066986.

Added k.regular.game().

Use vertex names to plot if no labels are specified in the function
call or as vetex attributes. Fixes issue #1085431.

power.law.fit() can now use a C implementation.

Fixed a bug in barabasi.game() when out.seq was an empty vector.

Fixed a bug that made functions with a progress bar fail if called
from another package.

Fixed a bug when creating graphs from a weighted integer adjacency
matrix via graph.adjacency(). Bug #1019624.

Fixed overflow issues in centralization calculations.

Fixed a minimal.st.separators() bug, some vertex sets were incorrectly
reported as separators. Bug #1033045.

Fixed a bug that mishandled vertex colors in VF2 isomorphism
functions. Bug #1032819.

Pajek exporter now always quotes strings, thanks to Elena Tea Russo.

Fixed a bug with handling small edge weights in shortest paths
calculation in shortest.paths() (Dijkstra's algorithm.) Thanks to
Martin J Reed.

Weighted transitivity uses V(graph) as 'vids' if it is NULL.

Fixed a bug when 'pie' vertices were drawn together with other
vertex shapes.

Speed up printing graphs.

Speed up attribute queries and other basic operations, by avoiding
copying of the graph. Bug #1043616.

Fixed a bug in the NCV setting for ARPACK functions. It cannot be
bigger than the matrix size.

layout.merge()'s DLA mode has better defaults now.

Fixed a bug in layout.mds() that resulted vertices on top of each
other.

Fixed a bug in layout.spring(), it was not working properly.

Fixed layout.svd(), which was completely defunct.

Fixed a bug in layout.graphopt() that caused warnings and on
some platforms crashes.

Fixed community.to.membership(). Bug #1022850.

Fixed a graph.incidence() crash if it was called with a nonmatrix
argument.

Fixed a get.shortest.paths bug, when output was set to "both".

Motif finding functions return NA for isomorphism classes that are
not motifs (i.e. not connected). Fixes bug #1050859.

Fixed get.adjacency() when attr is given, and the attribute has some
complex type. Bug #1025799.

Fixed attribute name in graph.adjacency() for dense matrices. Bug
#1066952.

Fixed erratic behavior of alpha.centrality().

Fixed igraph indexing, when attr is given. Bug #1073705.

Fixed a bug when calculating the largest cliques of a directed
graph. Bug #1073800.

Fixed a bug in the maximal clique search, closes #1074402.

Warn for negative weights when calculating PageRank.

Fixed dense, unweighted graph.adjacency when diag=FALSE. Closes
issue #1077425.

Fixed a bug in eccentricity() and radius(), the results were often
simply wrong.

Fixed a bug in get.all.shortest.paths() when some edges had zero weight.

graph.data.frame() is more careful when vertex names are numbers, to
avoid their scientific notation. Fixes issue #1082221.

Better check for NAs in vertex names. Fixes issue #1087215

Fixed a potential crash in the DrL layout generator.

Fixed a bug in the ReingoldTilford layout when the graph is
directed and mode != ALL.
Released June 11, 2012
See also the release notes at
http://igraph.sf.net/relnotes0.6.html
 Vertices and edges are numbered from 1 instead of 0.
Note that this makes most of the old R igraph code incompatible
with igraph 0.6. If you want to use your old code, please use
the igraph0 package. See more at http://igraph.sf.net/relnotes0.6.html.
 The '[' and '[[' operators can now be used on igraph graphs,
for '[' the graph behaves as an adjacency matrix, for '[[' is
is treated as an adjacency list. It is also much simpler to
manipulate the graph structure, i.e. add/remove edges and vertices,
with some new operators. See more at ?graph.structure.
 In all functions that take a vector or list of vertices or edges,
vertex/edge names can be given instead of the numeric ids.
 New package 'igraphdata', contains a number of data sets that can
be used directly in igraph.
 Igraph now supports loading graphs from the Nexus online data
repository, see nexus.get(), nexus.info(), nexus.list() and
nexus.search().
 All the community structure finding algorithm return a 'communities'
object now, which has a bunch of useful operations, see
?communities for details.
 Vertex and edge attributes are handled much better now. They
are kept whenever possible, and can be combined via a flexible API.
See ?attribute.combination.
 R now prints igraph graphs to the screen in a more structured and
informative way. The output of summary() was also updated
accordingly.
 It is possible to mark vertex groups on plots, via
shading. Communities and cohesive blocks are plotted using this by
default.
 Some igraph demos are now available, see a list via
'demo(package="igraph")'.
 igraph now tries to select the optimal layout algorithm, when
plotting a graph.
 Added a simple console, using Tcl/Tk. It contains a text area
for status messages and also a status bar. See igraph.console().
 Reimplemented igraph options support, see igraph.options() and
getIgraphOpt().
 Igraph functions can now print status messages.
 The multilevel modularity optimization community structure detection
algorithm by Blondel et al. was added, see multilevel.community().
 Distance between two community structures: compare.communities().
 Community structure via exact modularity optimization,
optimal.community().
 Hierarchical random graphs and community finding, porting the code
from Aaron Clauset. See hrg.game(), hrg.fit(), etc.
 Added the InfoMAP community finding method, thanks to Emmanuel
Navarro for the code. See infomap.community().
 Eccentricity (eccentricity()), and radius (radius()) calculations.
 Shortest path calculations with get.shortest.paths() can now
return the edges along the shortest paths.
 get.all.shortest.paths() now supports edge weights.
 Centralization scores for degree, closeness, betweenness and
eigenvector centrality. See centralization.scores().
 Personalized PageRank scores, see page.rank().
 Subgraph centrality, subgraph.centrality().
 Authority (authority.score()) and hub (hub.score()) scores support
edge weights now.
 Support edge weights in betweenness and closeness calculations.
 bonpow(), Bonacich's power centrality and alpha.centrality(),
Alpha centrality calculations now use sparse matrices by default.
 Eigenvector centrality calculation, evcent() now works for
directed graphs.
 Betweenness calculation can now use arbitrarily large integers,
this is required for some latticelike graphs to avoid overflow.
 Support the DL file format in graph.read(). See
http://www.analytictech.com/networks/dataentry.htm.
 Support writing the LEDA file format in write.graph().
 Star layout: layout.star().
 Layout based on multidimensional scaling, layout.mds().
 New layouts layout.grid() and layout.grid.3d().
 Sugiyama layout algorithm for layered directed acyclic graphs,
layout.sugiyama().
 New graph generators: static.fitness.game(), static.power.law.game().
 barabasi.game() was rewritten and it supports three algorithms now,
the default algorithm does not generate multiple or loop edges.
The graph generation process can now start from a supplied graph.
 The WattsStrogatz graph generator, igraph_watts_strogatz() can
now create graphs without loop edges.
 Added the Spectral Coarse Graining algorithm, see scg().
 The cohesive.blocks() function was rewritten in C, it is much faster
now. It has a nicer API, too. See demo("cohesive").
 Added generic breadthfirst and depthfirst search implementations
with many callbacks, graph.bfs() and graph_dfs().
 Support vertex and edge coloring in the VF2 (sub)graph isomorphism
functions (graph.isomorphic.vf2(), graph.count.isomorphisms.vf2(),
graph.get.isomorphisms.vf2(), graph.subisomorphic.vf2(),
graph.count.subisomorphisms.vf2(), graph.get.subisomorphisms.vf2()).
 Assortativity coefficient, assortativity(), assortativity.nominal()
and assortativity.degree().
 Vertex operators that work by vertex names:
graph.intersection.by.name(), graph.union.by.name(),
graph.difference.by.name(). Thanks to Magnus Torfason for
contributing his code!
 Function to calculate a noninduced subraph: subgraph.edges().
 More comprehensive maximum flow and minimum cut calculation,
see functions graph.maxflow(), graph.mincut(), stCuts(), stMincuts().
 Check whether a directed graph is a DAG, is.dag().
 has.multiple() to decide whether a graph has multiple edges.
 Added a function to calculate a diversity score for the vertices,
graph.diversity().
 Graph Laplacian calculation (graph.laplacian()) supports edge
weights now.
 Biconnected component calculation, biconnected.components()
now returns the components themselves.
 bipartite.projection() calculates multiplicity of edges.
 Maximum cardinality search: maximum.cardinality.search() and
chordality test: is.chordal()
 Convex hull computation, convex.hull().
 Contract vertices, contract.vertices().
Released November 22, 2009
 Some small changes to make 'R CMD check' clean
 Fixed a bug in graph.incidence, the 'directed' and 'mode' arguments
were not handled correctly
 Betweenness and edge betweenness functions work for graphs with
many shortest paths now (up to the limit of long long int)
 When compiling the package, the configure script fails if there is
no C compiler available
 igraph.from.graphNEL creates the right number of loop edges now
 Fixed a bug in bipartite.projection() that caused occasional crashes
on some systems
Released April 10, 2009
See also the release notes at
http://igraph.sf.net/relnotes0.5.2.html
 Added progress bar support to beweenness() and
betweenness.estimate(), layout.drl()
 Speeded up betweenness estimation
 Speeded up are.connected()
 Johnson's shortest paths algorithm added
 shortest.paths() has now an 'algorithm' argument to choose from the
various implementations manually
 Always quote symbolic vertex names when printing graphs or edges
 Average nearest neighbor degree calculation, graph.knn()
 Weighted degree (also called strength) calculation, graph.strength()
 Some new functions to support bipartite graphs: graph.bipartite(),
is.bipartite(), get.indicence(), graph.incidence(),
bipartite.projection(), bipartite.projection.size()
 Support for plotting curved edges with plot.igraph() and tkplot()
 Added support for weighted graphs in alpha.centrality()
 Added the label propagation community detection algorithm by
Raghavan et al., label.propagation.community()
 cohesive.blocks() now has a 'cutsetHeuristic' argument to choose
between two cutset algorithms
 Added a function to "unfold" a tree, unfold.tree()
 New tkplot() arguments to change the drawing area
 Added a minimal GUI, invoke it with tkigraph()
 The DrL layout generator, layout.drl() has a three dimensional mode
now.
 Fixed a bug in VF2 graph isomorphism functions
 Fixed a bug when a sparse adjacency matrix was requested in
get.adjacency() and the graph was named
 VL graph generator in degree.sequence.game() checks now that
the sum of the degrees is even
 Many fixes for supporting various compilers, e.g. GCC 4.4 and Sun's
C compiler
 Fixed memory leaks in graph.automorphisms(), BellmanFord
shortest.paths(), independent.vertex.sets()
 Fix a bug when a graph was imported from LGL and exported to NCOL
format (#289596)
 cohesive.blocks() creates its temporary file in the session
temporary directory
 write.graph() and read.graph() now give error messages when unknown
arguments are given
 The GraphML reader checks the name of the attributes to avoid adding
a duplicate 'id' attribute
 It is possible to change the 'ncv' ARPACK parameter for
leading.eigenvector.community()
 Fixed a bug in path.length.hist(), 'unconnected' was wrong
for unconnected and undirected graphs
 Better handling of attribute assingment via iterators, this is now
also clarified in the manual
 Better error messages for unknown vertex shapes
 Make R package unload cleanly if unloadNamespace() is used
 Fixed a bug in plotting square shaped vertices (#325244)
 Fixed a bug in graph.adjacency() when the matrix is a sparse matrix
of class "dgTMatrix"
Released July 14, 2008
See also the release notes at
http://igraph.sf.net/relnotes0.5.1.html
 A new layout generator called DrL.
 Uniform sampling of random connected undirected graphs with a
given degree sequence.
 Edge labels are plotted at 1/3 of the edge, this is better if
the graph has mutual edges.
 Initial and experimental vertex shape support in 'plot'.
 New function, 'graph.adjlist' creates igraph graphs from
adjacency lists.
 Conversion to/from graphNEL graphs, from the 'graph' R package.
 Fastgreedy community detection can utilize edge weights now, this
was missing from the R interface.
 The 'arrow.width' graphical parameter was added.
 graph.data.frame has a new argument 'vertices'.
 graph.adjacency and get.adjacency support sparse matrices,
the 'Matrix' package is required to use this functionality.
 graph.adjacency adds column/row names as 'name' attribute.
 Weighted shortest paths using Dijkstra's or the BelmannFord
algorithm.
 Shortest path functions return 'Inf' for unreachable vertices.
 New function 'is.mutual' to find mutual edges in a directed graph.
 Added inverse logweighted similarity measure (a.k.a. Adamic/Adar
similarity).
 preference.game and asymmetric.preference.game were
rewritten, they are O(V+E) now, instead of O(V^2).
 Edge weight support in function 'get.shortest.paths', it uses
Dijkstra's algorithm.
 A bug was corrected in write.pajek.bgraph.
 Several bugs were corrected in graph.adjacency.
 Pajek reader bug corrected, used to segfault if '*Vertices'
was missing.
 Directedness is handled correctly when writing GML files.
(But note that 'correct' conflicts the standard here.)
 Corrected a bug when calculating weighted, directed PageRank on an
undirected graph. (Which does not make sense anyway.)
 Several bugs were fixed in the ReingoldTilford layout to avoid
edge crossings.
 A bug was fixed in the GraphML reader, when the value of a graph
attribute was not specified.
 Fixed a bug in the graph isomorphism routine for small (34 vertices)
graphs.
 Corrected the random sampling implementation (igraph_random_sample),
now it always generates unique numbers. This affects the
Gnm ErdosRenyi generator, it always generates simple graphs now.
 The basic igraph constructor (igraph_empty_attrs, all functions
are expected to call this internally) now checks whether the number
of vertices is finite.
 The LGL, NCOL and Pajek graph readers handle errors properly now.
 The nonsymmetric ARPACK solver returns results in a consistent form
now.
 The fast greedy community detection routine now checks that the graph
is simple.
 The LGL and NCOL parsers were corrected to work with all
kinds of endofline encodings.
 Hub & authority score calculations initialize ARPACK parameters now.
 Fixed a bug in the Walktrap community detection routine, when applied
to unconnected graphs.
 Several small memory leaks were removed, and a big one from the Spinglass
community structure detection function
Released February 14, 2008
See also the release notes at http://igraph.sf.net/relnotes0.5.html

The 'rescale', 'asp' and 'frame' graphical parameters were added

Create graphs from a formula notation (graph.formula)

Handle graph attributes properly

Calculate the actual minimum cut for undirected graphs

Adjacency lists, get.adjlist and get.adjedgelist added

Eigenvector centrality computation is much faster now

Proper R warnings, instead of writing the warning to the terminal

R checks graphical parameters now, the unknown ones are not just
ignored, but an error message is given

plot.igraph has an 'add' argument now to compose plots with multiple
graphs

plot.igraph supports the 'main' and 'sub' arguments

layout.norm is public now, it can normalize a layout

It is possible to supply startup positions to layout generators

Always free memory when CTRL+C/ESC is pressed, in all operating
systems

plot.igraph can plot square vertices now, see the 'shape' parameter

graph.adjacency rewritten when creating weighted graphs

We use match.arg whenever possible. This means that character scalar
options can be abbreviated and they are always case insensitive

VF2 graph isomorphism routines can check subgraph isomorphism now,
and they are able to return matching(s)

The BLISS graph isomorphism algorithm is included in igraph now. See
canonical.permutation, graph.isomorphic.bliss

We use ARPACK for eigenvalue/eigenvector calculation. This means that the
following functions were rewritten: page.rank,
leading.eigenvector.community.*, evcent. New functions based on
ARPACK: hub.score, authority.score, arpack.

Edge weights for FruchtermanReingold layout (layout.fruchterman.reingold).

Line graph calculation (line.graph)

Kautz and de Bruijn graph generators (graph.kautz, graph.de.bruijn)

Support for writing graphs in DOT format

Jaccard and Dice similarity coefficients added (similarity.jaccard,
similarity.dice)

Counting the multiplicity of edges (count.multiple)

The graphopt layout algorithm was added, layout.graphopt

Generation of "famous" graphs (graph.famous).

Create graphs from LCF notation (graph.cf).

Dyad census and triad cencus functions (dyad.census, triad.census)

Cheking for simple graphs (is.simple)

Create full citation networks (graph.full.citation)

Create a histogram of path lengths (path.length.hist)

Forest fire model added (forest.fire.game)

DIMACS reader can handle different file types now

Biconnected components and articulation points (biconnected.components,
articulation.points)

Kleinberg's hub and authority scores (hub.score, authority.score)

as.undirected handles attributes now

Geometric random graph generator (grg.game) can return the
coordinates of the vertices

Function added to convert leading eigenvector community structure result to
a membership vector (community.le.to.membership)

Weighted fast greedy community detection

Weighted page rank calculation

Functions for estimating closeness, betweenness, edge betweenness by
introducing a cutoff for path lengths (closeness.estimate,
betweenness.estimate, edge.betweenness.estimate)

Weighted modularity calculation

Function for permuting vertices (permute.vertices)

Betweenness and closeness calculations are speeded up

read.graph can handle all possible line terminators now (\r, \n, \r\n, \n\r)

Error handling was rewritten for walktrap community detection,
the calculation can be interrupted now

The maxflow/mincut functions allow to supply NULL pointer for edge
capacities, implying unit capacities for all edges
 Fixed a bug in cohesive.blocks, cohesive blocks were sometimes not
calculated correctly
Released January 1, 2008
New:
 Cohesive block finding in the R interface, thanks to Peter McMahan
for contributing his code. See James Moody and Douglas R. White,
2003, in Structural Cohesion and Embeddedness: A Hierarchical
Conception of Social Groups American Sociological Review 68(1):125
 Biconnected components and articulation points.
 R interface: better printing of attributes.
 R interface: graph attributes can be used via '$'.
Bug fixed:
 ErdosRenyi random graph generators rewritten.
Released October 3, 2007
This release should work seemlessly with the new R 2.6.0 version.
Some other bugs were also fixed:
 A bug was fixed in the ErdosRenyi graph generator, which sometimes
added an extra vertex.
Released August 13, 2007
The next one in the sequence of bugfix releases. Thanks to many people
sending bug reports. Here are the changes:
 Some memory leaks removed when using attributes from R or Python.
 GraphML parser: entities and character data in multiple chunks are
now handled correctly.
 A bug corrected in edge betweenness community structure detection,
it failed if called many times from the same program/session.
 Edge betweeness community structure: handle unconnected graphs properly.
 Fixed bug related to fast greedy community detection in unconnected graphs.
 Use a different kind of parser (Push) for reading GraphML
files. This is almost invisible for users but fixed a
nondeterministic bug when reading in GraphML files.
 R interface: plot now handles properly if called with a vector as
the edge.width argument for directed graphs.
 R interface: bug (typo) corrected for walktrap.community and
weighted graphs.
Released June 7, 2007
This is another bugfix release, as there was a serious bug in the
R package of the previous version: it could not read and write graphs
to files in any format under MS Windows.
Some other bits added:
 circular ReingoldTilford layout generator for trees
 corrected a bug, Pajek files are written properly under MS Windows now.
 arrow.size graphical edge parameter added in the R interface.
Released May 23, 2007
This is a minor release, it corrects a number of bugs, mostly in the
R package.
Released May 21, 2007
The major new additions in this release is a bunch of community
detection algorithms and support for the GML file format. Here
is the complete list of changes:

as the internal representation changed, graphs stored with 'save'
with an older igraph version cannot be read back with the new
version reliably.

neighbors returns ordered lists

is.loop and is.multiple were added

topological sorting

VF2 isomorphism algorithm

support for reading graphs from the Graph Database for isomorphism

graph.mincut can calculate the actual minimum cut

girth calculation added, thanks to Keith Briggs

support for reading and writing GML files

Walktrap community detection algorithm added, thanks to Matthieu Latapy
and Pascal Pons

edge betweenness based community detection algorithm added

fast greedy algorithm for community detection by Clauset et al. added
thanks to Aaron Clauset for sharing his code

leading eigenvector community detection algorithm by Mark Newman added

functions for creating dendrograms from the output of the
community detection algorithms added

community.membership supporting function added, creates
a membership vector from a community structure merge tree

modularity calculation added

graphics parameter handling is completely rewritten, uniform handling
of colors and fonts, make sure you read ?igraph.plotting

new plotting parameter for edges: arrow.mode

a bug corrected when playing a nonlinear barabasi.game

better looking plotting in 3d using rglplot: edges are 3d too

rglplot layout is allowed to be two dimensional now

rglplot suspends updates while drawing, this makes it faster

loop edges are correctly plotted by all three plotting functions

better printing of attributes when printing graphs

summary of a graph prints attribute names

is.igraph rewritten to make it possible to inherit from the 'igraph' class

somewhat better looking progress meter for functions which support it
 many functions benefit from the new internal representation and are
faster now: transitivity, reciprocity, graph operator functions like
intersection and union, etc.
 corrected a bug when reading Pajek files: directed graphs were read
as undirected
Released Dec 19, 2006
This is a new major release, it contains many new things:
 bonpow function ported from SNA to calculate Bonacich power centrality
 get.adjacency supports attributes now, this means that it sets the
colnames and rownames attributes and can return attribute values in
the matrix instead of 0/1
 grg.game, geometric random graphs
 graph.density, graph density calculation
 edge and vertex attributes can be added easily now when added new
edges with add.edges or new vertices with add.vertices
 graph.data.frame creates graph from data frames, this can be used to
create graphs with edge attributes easily
 plot.igraph and tkplot can plot selfloop edges now
 graph.edgelist to create a graph from an edge list, can also handle
edge lists with symbolic names
 get.edgelist has now a 'names' argument and can return symbolic
vertex names instead of vertex ids, by default id uses the 'name'
vertex attribute is returned
 printing graphs on screen also prints symbolic symbolic names
(the 'name' attribute if present)
 maximum flow and minimum cut functions: graph.maxflow, graph.mincut
 vertex and edge connectivity: edge.connectivity, vertex.connectivity
 edge and vertex disjoint paths: edge.disjoint.paths,
vertex.disjoint.paths
 White's cohesion and adhesion measure: graph.adhesion, graph.cohesion
 dimacs file format added
 as.directed handles attributes now
 constraint corrected, it handles weighted graphs as well now
 weighted attribute to graph.adjacency
 spinglassbased community structure detection, the Joerg Reichardt 
Stefan Bornholdt algorithm added: spinglass.community
 graph.extended.chordal.ring, extended chordal ring generation
 no.clusters calculates the number of clusters without calculating
the clusters themselves
 minimum spanning tree functions updated to keep attributes
 transitivity can calculate local transitivity as well
 neighborhood related functions added: neighborhood,
neighborhood.size, graph.neighborhood
 new graph generators based on vertex types: preference.game and
asymmetric.preference.game
 attribute handling bug when deleting edges corrected
 GraphML escaping and NaN handling corrected
 bug corrected to make it possible compile the R package without the
libxml2 library
 a bug in ErdosRenyi graph generation corrected: it had problems
with generating large directed graphs
 bug in constraint calculation corrected, it works well now
 fixed memory leaks in the GraphML reader
 error handling bug corrected in the GraphML reader
 bug corrected in R version of graph.laplacian when normalized
Laplacian is requested
 memory leak corrected in get.all.shortest.paths in the R package
Released Aug 23, 2006
This is a bugfix release. Bugs fixed:
 reciprocity corrected to avoid segfaults
 some docs updates
 various R package updates to make it conform to the CRAN rules
Released Aug 18, 2006
Release time at last! There are many new things in igraph 0.2, the
most important ones:
 reading writing Pajek and GraphML formats with attributes
(not all Pajek and GraphML files are supported, see documentation
for details)
 the RANDEDU fast motif search algorithm is implemented
 many new graph generators, both games and regular graphs
 many new structural properties: transitivity, reciprocity, etc.
 graph operators: union, intersection, difference, structural holes, etc.
 conversion between directed and undirected graphs
 new layout algorithms for trees and large graphs, 3D layouts
and many more.
New things specifically in the R package:
 support for CTRL+C
 new functions: Graph Laplacian, Burt's constraint, etc.
 vertex/edge sequences totally rewritten, smart indexing (see manual)
 new R manual and tutorial: `Network Analysis with igraph', still
under development but useful
 very basic 3D plotting using OpenGL
Although this release was somewhat tested on Linux, MS Windows, Mac
OSX, Solaris 8 and FreeBSD, no heavy testing was done, so it might
contain bugs, and we kindly ask you to send bug reports to make igraph
better.
Released Jan 30, 2006
After about a year of development this is the first "official" release
of the igraph library. This release should be considered as beta
software, but it should be useful in general. Please send your
questions and comments.