Errata

Page 159-172:
The Rintact package has been deprecated and all its functionalty has moved to the RpsiXML package. The whole chapter has been edited to reflect these changes.
Page 183:
All node- and edge-specific layout attributes can now be set using the nodeRenderInfo and edgeRenderInfo functions. There is no need to supply those as additional attributes to layoutGraph. Some of the code chunks have been updated accordingly.