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# Create an array with ones at and below the given diagonal and zeros elsewhere in Numpy

To create an array with ones at and below the given diagonal and zeros elsewhere, use the **numpy.tri()** method in Python Numpy −

- The 1st parameter is the number of rows in the array
- The 2nd parameter is the number of columns in the array

The tri() function returns an array with its lower triangle filled with ones and zero elsewhere; in other words T[i,j] == 1 for j <= i + k, 0 otherwise.

## Steps

At first, import the required library −

import numpy as np

Now, create an array with ones at and below the given diagonal and zeros elsewhere using the numpy.tri() method in Python Numpy −

arr = np.tri(4, 4)

Displaying our array −

print("Array...\n",arr)

Get the datatype −

print("\nArray datatype...\n",arr.dtype)

Get the dimensions of the Array −

print("\nArray Dimensions...\n",arr.ndim)

Get the shape of the Array −

print("\nOur Array Shape...\n",arr.shape)

Get the number of elements of the Array −

print("\nElements in the Array...\n",arr.size)

## Example

import numpy as np # To create an array with ones at and below the given diagonal and zeros elsewhere, use the numpy.tri() method in Python Numpy # The 1st parameter is the number of rows in the array # The 2nd parameter is the number of columns in the array arr = np.tri(4, 4) # Displaying our array print("Array...\n",arr) # Get the datatype print("\nArray datatype...\n",arr.dtype) # Get the dimensions of the Array print("\nArray Dimensions...\n",arr.ndim) # Get the shape of the Array print("\nOur Array Shape...\n",arr.shape) # Get the number of elements of the Array print("\nElements in the Array...\n",arr.size)

## Output

Array... [[1. 0. 0. 0.] [1. 1. 0. 0.] [1. 1. 1. 0.] [1. 1. 1. 1.]] Array datatype... float64 Array Dimensions... 2 Our Array Shape... (4, 4) Elements in the Array... 16

- Related Questions & Answers
- Create an array with ones below the main diagonal and zeros elsewhere in Numpy
- Create an array with ones at and below the given diagonal and zeros elsewhere with a different output type in Numpy
- Create an array with ones above the main diagonal and zeros elsewhere in Numpy
- Return a 2-D array with ones on the diagonal and zeros elsewhere in Numpy
- Return a 2-D array with ones on the upper diagonal and zeros elsewhere in Numpy
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- Return a 2-D array with ones on the diagonal and zeros elsewhere and also set the number of columns in Numpy
- Return a 2-D array with ones on the diagonal and zeros elsewhere but set a different datatype in Numpy
- Return the Lower triangle of an array and zero elements just below the main diagonal in Numpy
- Return an array of ones with the same shape and type as a given array in Numpy
- Return an array of zeros with the same shape and type as a given array in Numpy
- Create a two-dimensional array with the flattened input as an upper diagonal in Numpy
- Return a new array of given shape filled with ones in Numpy
- Create an array with zero above the main diagonal forming a lower triangular matrix in Numpy
- Return a new array of given shape filled with ones and also set the desired data-type in Numpy

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