Access upper triangular matrix elements stored in a single row vector - testing in MATLAB implementation - http://tibor-simon.com/programming/access-upper-triangular-matrix-elements-stored-in-a-single-row-vector/

transformation_test.m

%% Testing th ij2l function

%% Let the upper trinagle matrix be
% 
%     | 1 2 3 |
% A = |   4 5 |
%     |     6 |
%
% We want to index the second row, last element:
%
%     | 1 2 3 |
% A = |   4(5)|
%     |     6 |

n = 3;
i = 2;
j = 3;

l = ij2l(i,j,n);

v = [1 2 3 4 5 6];

v(l)