NumPy | tri method
Start your free 7-days trial now!
Numpy's tri(~)
method creates a 2D Numpy array that represents a lower triangular matrix. The values at and below the main diagonal are filled with 1s, while everywhere else with 0s.
Parameters
1. N
| int
The number of rows of the resulting array.
2. M
| int
| optional
The number of columns of the resulting array. By default, M=N
.
3. k
link | int
| optional
The number of diagonals to exclude or include.
A positive value for k
represents inclusion. k=1
means that we include an additional diagonal on top of main diagonal.
A negative value for k
represents exclusion. k=-1
means that the main diagonal is excluded. k=-2
means that the main diagonal and the diagonal underneath are excluded.
By default, k=0
, which means that a perfect lower triangle is returned.
4. dtype
| string
or type
| optional
The data type of the resulting array. By default, dtype=float
.
Return value
A Numpy array representing a lower triangular matrix.
Examples
Basic usage
To create a 3 by 3 lower triangular matrix:
np.tri(3)
array([[ 1., 0., 0.], [ 1., 1., 0.], [ 1., 1., 1.]])
To create a 3 by 4 lower triangular matrix of type int
:
np.tri(3, 4, dtype=int)
array([[1, 0, 0, 0], [1, 1, 0, 0], [1, 1, 1, 0]])
Specifying a positive k
To include an additional diagonal, set k=1
:
np.tri(3, k=1, dtype=int)
array([[1, 1, 0], [1, 1, 1], [1, 1, 1]])
Specifying a negative k
To exclude the main diagonal, set k=-1
:
np.tri(3, k=-1)
array([[ 0., 0., 0.], [ 1., 0., 0.], [ 1., 1., 0.]])