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Functions for diallel cross data


Diallel cross is a widely used genetic design that is made of all possible crosses (combinations) among a set of parents (inbreds or varieties). Diallel cross data are used to study the inheritance of a trait among the set of parents. For quantitative traits, general and specific combining ability (GCA and SCA) often are the statistics used to characterize the parents and their combinations. 


A diallel cross dataset is a two-way table, each parent being both an entry and a tester. The parent per se values are the diagonal elements of the two-way table. The following can be achieved through GGE biplot analysis of a diallel cross dataset:

Evaluation of parents as entries

Evaluation of parents as testers


Note: If you are only interested in understanding the entry-by-tester interactions, i.e., biplot based on double-centered data, should be used. However, I don't see how such analysis can be of any value.