CODE EXAMPLE FOR PYTHON

converting 1d array into upper triangular

In [680]: ind = np.triu_indices(4)
In [681]: values = np.arange(16).reshape(4,4)[ind]
In [682]: result = np.zeros((4,4),int)
In [683]: result[ind]=values
In [684]: values
Out[684]: array([ 0,  1,  2,  3,  5,  6,  7, 10, 11, 15])
In [685]: result
Out[685]: 
array([[ 0,  1,  2,  3],
       [ 0,  5,  6,  7],
       [ 0,  0, 10, 11],
       [ 0,  0,  0, 15]])