# jax.numpy.diagonal#

jax.numpy.diagonal(a, offset=0, axis1=0, axis2=1)[source]#

Return specified diagonals.

LAX-backend implementation of `numpy.diagonal()`.

The JAX version of this function may in some cases return a copy rather than a view of the input.

Original docstring below.

If a is 2-D, returns the diagonal of a with the given offset, i.e., the collection of elements of the form `a[i, i+offset]`. If a has more than two dimensions, then the axes specified by axis1 and axis2 are used to determine the 2-D sub-array whose diagonal is returned. The shape of the resulting array can be determined by removing axis1 and axis2 and appending an index to the right equal to the size of the resulting diagonals.

In versions of NumPy prior to 1.7, this function always returned a new, independent array containing a copy of the values in the diagonal.

In NumPy 1.7 and 1.8, it continues to return a copy of the diagonal, but depending on this fact is deprecated. Writing to the resulting array continues to work as it used to, but a FutureWarning is issued.

Starting in NumPy 1.9 it returns a read-only view on the original array. Attempting to write to the resulting array will produce an error.

In some future release, it will return a read/write view and writing to the returned array will alter your original array. The returned array will have the same type as the input array.

If you donâ€™t write to the array returned by this function, then you can just ignore all of the above.

If you depend on the current behavior, then we suggest copying the returned array explicitly, i.e., use `np.diagonal(a).copy()` instead of just `np.diagonal(a)`. This will work with both past and future versions of NumPy.

Parameters:
• a (array_like) â€“ Array from which the diagonals are taken.

• offset (int, optional) â€“ Offset of the diagonal from the main diagonal. Can be positive or negative. Defaults to main diagonal (0).

• axis1 (int, optional) â€“ Axis to be used as the first axis of the 2-D sub-arrays from which the diagonals should be taken. Defaults to first axis (0).

• axis2 (int, optional) â€“ Axis to be used as the second axis of the 2-D sub-arrays from which the diagonals should be taken. Defaults to second axis (1).

Returns:

array_of_diagonals â€“ If a is 2-D, then a 1-D array containing the diagonal and of the same type as a is returned unless a is a matrix, in which case a 1-D array rather than a (2-D) matrix is returned in order to maintain backward compatibility.

If `a.ndim > 2`, then the dimensions specified by axis1 and axis2 are removed, and a new axis inserted at the end corresponding to the diagonal.

Return type:

ndarray