The kinship2 R package for pedigree data.

BACKGROUND The kinship2 package is restructured from the previous kinship package. Existing features are now enhanced and new features added for handling pedigree objects. METHODS Pedigree plotting features have been updated to display features on complex pedigrees while adhering to pedigree plotting standards. Kinship matrices can now be calculated for the X chromosome. Other methods have been added to subset and trim pedigrees while maintaining the pedigree structure. CONCLUSION We make the kinship2 package available for R on the Contributed R Archives Network (CRAN), where data management is built-in and other packages can use the pedigree object.