Linear indexing in symmetric matrices

Question

We can access matrices using linear indexing, which follows this pattern

0 1 2

3 4 5

6 7 8

It\'s easy to get the i,j coordinates for this cas

Answer 1

Since nobody has posted a Matlab solution yet, here's a simple one-liner:

idxs = find(triu(true(size(A))))

Given matrix A, this will return a vector of all your indices, such that idxs(k) returns the k-th linear index into the upper triangular portion of the matrix.