Vectorization operations on matrices

Functions
vector	lower_elements (matrix mat)

Detailed Description

 
vector lower_elements(matrix mat) {
  int N = rows(mat);
  int K = (N * (N - 1)) %/% 2;
  vector[K] out;
  
  int count = N;
  int pos = 1;
  
  for (k in 1 : N - 1) {
    count -= 1;
    out[pos : pos + count - 1] = sub_col(mat, k + 1, k, count);
    pos += count;
  }
  
  return out;
}

Function Documentation

lower_elements()

vector lower_elements

(

matrix

mat

)

The strictly lower triangular elements of a matrix.

Copyright 2025, Sean Pinkney

Parameters

mat	Matrix
vector	of lower triangular elements