Position in a vector of linear independent values

Returns the position of the [i,j]th element of a symmetric n \(\times\) n matrix that this element has in a vector of the linear independent values of the matrix.

veclipos( i, j, n )

Arguments

i

row of the element in the matrix.

j

column of the element in the matrix.

n

dimension of the matrix.

Note

A symmetric n \(\times\) n matrix has n*(n+1)/2 independent values.
The function is: n*(n-1)/2-((n-min(i,j))*(n-min(i,j)+1)/2)+max(i,j)

See also

vecli, vecli2m.

Author

Arne Henningsen

Examples

   veclipos( 1, 2, 3 )  # returns: 2
#> [1] 2