pub fn ground_at(matrix: &CsMat<f64>, r: usize) -> CsMat<f64>Expand description
Delete row r and column r from a square matrix, returning the
(n−1)×(n−1) grounded matrix. Used to remove the slack bus so a singular
Laplacian becomes SPD. The single-reference case of ground_at_each.
§Panics
Panics if r >= matrix.rows(): with no row/column to remove the result
would be silently the wrong shape.