/// <summary>
/// An array with ones at and below the given diagonal and zeros elsewhere.
/// </summary>
/// <param name="N">Number of rows in the array.</param>
/// <param name="M">Number of columns in the array.</param>
/// <param name="k">The sub-diagonal at and below which the array is filled.'k' = 0 is the main diagonal, while 'k' LT 0 is below it, and 'k' GT 0 is above.The default is 0.</param>
/// <param name="dtype">Data type of the returned array. The default is float.</param>
/// <returns></returns>
public static ndarray tri(int N, int?M = null, int k = 0, dtype dtype = null)
{
/*
* An array with ones at and below the given diagonal and zeros elsewhere.
*
* Parameters
* ----------
* N : int
* Number of rows in the array.
* M : int, optional
* Number of columns in the array.
* By default, `M` is taken equal to `N`.
* k : int, optional
* The sub-diagonal at and below which the array is filled.
* `k` = 0 is the main diagonal, while `k` < 0 is below it,
* and `k` > 0 is above. The default is 0.
* dtype : dtype, optional
* Data type of the returned array. The default is float.
*
* Returns
* -------
* tri : ndarray of shape (N, M)
* Array with its lower triangle filled with ones and zero elsewhere;
* in other words ``T[i,j] == 1`` for ``i <= j + k``, 0 otherwise.
*
* Examples
* --------
* >>> np.tri(3, 5, 2, dtype=int)
* array([[1, 1, 1, 0, 0],
* [1, 1, 1, 1, 0],
* [1, 1, 1, 1, 1]])
*
* >>> np.tri(3, 5, -1)
* array([[ 0., 0., 0., 0., 0.],
* [ 1., 0., 0., 0., 0.],
* [ 1., 1., 0., 0., 0.]])
*/
if (dtype == null)
{
dtype = np.Float32;
}
if (M == null)
{
M = N;
}
ndarray m = ufunc.outer(UFuncOperation.greater_equal, np.Bool, arange(N, dtype: _min_int(0, N)),
arange(-k, M - k, dtype: _min_int(-k, (int)M - k)));
// Avoid making a copy if the requested type is already bool
m = m.astype(dtype, copy: false);
return(m);
}