Calculates the cross-product of the design matrix X with the vertex chunk Y (XtY),
along with the sum (1'Y) and sum of squares (Y'Y) for each vertex in the chunk.
Arguments
- X
Numeric matrix. The design matrix of dimension \(n \times p\).
- ss_chunk
Numeric matrix. A chunk of the ss matrix of dimension \(n \times B\),
where B is the block size (number of vertices in the chunk).
Value
A list containing:
- XtY
A numeric matrix of dimension \(p \times B\), representing \(X^T Y\).
- psumsY
A numeric matrix of dimension \(2 \times B\). The first row contains
the column sums of Y (\(1^T Y\)), and the second row contains the column sums
of squared Y (\(Y^T Y\)).
Author
Serena Defina, 2026.
