G:
a numeric genotype matrix of 3400 individuals and 93 SNPs.
Each row represents a individual, and each column represents a SNP marker.
X:
a numeric matrix of covariates with the first column represents intercept, the second column represents a continuous covariate,
and the third column represents a binary covariate.
Z:
a numeric vector of 1s for the second level covariate.
Z.func:
a numeric matrix for the second level covariate. The first column contains all 1s, representing the intercept, and the second column
is 0 or 1, representing whether a SNP marker is functional or non-functional.
maf:
a numeric vector for the Minor Allele Frequecy of 93 SNPs.