Project z-scores of one LD block to another LD block

Project z-scores of one LD block to another LD block

project.zscore(ld.svd.tgt, ld.svd.src, z.src)

Arguments

ld.svd.tgt

SVD result on the target LD block

ld.svd.src

SVD result on the source LD block

z.src

z-score matrix of the source LD block

stdize

standardize if TRUE, otherwise just center the mean

Value

new z-score matrix

Details

We assume the estimated individual phenotype: $$\mathbf{y}_{src} \sim \mathcal{N}\!\left(U_{src}D_{src}^{-1}V_{src}^{\top}\mathbf{z}_{src}, I\right).$$ Therefore, a new z-score projected onto the target LD block will be: $$\mathbf{z}_{tgt} \sim \mathcal{N}\!\left(V_{tgt}D_{tgt}U_{tgt}^{\top}\mathbf{y}_{src}, V_{tgt}D_{tgt}^{2}V_{tgt}^{\top}\right).$$