Extract a diagonal or construct a diagonal matrix.
If a is 1-D then a diagonal matrix is constructed with a on the
\(k\)-th diagonal. If a is 2-D then the \(k\)-th diagonal is
returned.
- Parameters:
a (array) – 1-D or 2-D input array.
k (int, optional) – The diagonal to extract or construct.
Default: 0.
- Returns:
The extracted diagonal or the constructed diagonal matrix.
- Return type:
array
