weighted sum/difference of two regression vectors
fun_lines.Rd`fun_lines` applies function `fun` to regression vectors while reordering the coefficients, such that the `j`-th coefficient in `beta[j, ]` is permuted with the `i`-th coefficient.
Arguments
- i
- integer scalar. Index of the first vector. 
- j
- integer scalar. Index of the second vector. 
- beta
- p by p numeric matrix. In rows, regression vectors coefficients after node-wise regression. `diag(beta) = 0`. 
- fun
- function. Applied on lines. 
- ni
- integer scalar. Weight for vector `i`. 
- nj
- integer scalar. Weight for vector `j`.