keeps the heritability estimated from the null model fixed when testing individual SNPs. Their approach is implemented in the software EMMAX (EMMA eXpedited). (This approximation, and related ideas, was also considered by previous authors, including10,11.) Both these last two approximations have per-SNP computation time that increases quadratically with the number of individuals, which makes them practical, on a single desktop computer, for GWAS involving thousands of individuals.
