`isdiag`

Tests whether a matrix is diagonal.

Category: Mathematics > Linear Algebra

Syntax

tf = isdiag(A)

True if all entries off the main diagonal are zero.

Description

The diagonal entries themselves may be anything, including zero, so the zero matrix is diagonal. A rectangular matrix qualifies when everything outside the leading diagonal is zero. An empty matrix is diagonal.

Input arguments

A: Numeric or logical matrix; not necessarily square.

Output arguments

tf: Logical scalar.

Example

Three cases

isdiag(eye(3))
isdiag([1 2; 0 3])
isdiag([])

Output

ans = logical
   1
ans = logical
   0
ans = logical
   1

See also

isbanded istril istriu diag bandwidth