**What is a biplot **

The biplot was originally proposed by Gabriel (1971) as a graphical tool to present results from principal component analysis (PCA). It is a scatter plot that graphically displays a rank-2 matrix by *both *the rows (entries) and the columns (testers). Here "bi" means "both". A rank-2 matrix is a matrix that results from multiplying a matrix with 2 columns by a matrix with 2 rows. Most two-way tables are not a rank-2 matrix. However, if a two-way table can be sufficiently approximated by a rank-2 matrix, then it can be effectively investigated using a 2-D biplot. Likewise, a 3-D biplot can be used to effectively investigate a rank-3 matrix. Below is a 2-D biplot based on the genotype by environment data on this page:

In a biplot generated by GGEbiplot, the entries are by default labeled in title case and blue color, and the testers in upper case and red color. The accurate position of an entry or a tester is at the beginning of the label.

**In Depth**: