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# How to use the numpy.sign() method for 2D arrays in Python

Maria Elijah

## The numpy.sign() method

The sign() method in Python’s NumPy library returns the sign of each number of the input array. It is done element-wise.

### How does it work?

• If an element in the array x is greater than 0, the method returns 1 for that particular element.
• If an element in the array x is less than 0, the method returns -1 for that particular element.
• If an element in the array x is equal to 0, the method returns 0 for that particular element.
• For complex elements, if x.real!= 0, the sign() method returns sign(x.real) + 0j. Otherwise, it returns sign(x.imag) + 0j.

Note: In Python, a list of lists can be used to generate a two-dimensional (2D) array.

### Syntax

numpy.sign(x,out=None, where=True)


### Parameters

• x: This represents the input array.
• out: This specifies where the result is stored. This is an optional parameter.
• where: This represents the condition in which the input gets broadcasted. This is an optional parameter.

### Return value

The numpy.sign() method returns the sign of each number of the input array.

### Example

The following code demonstrates how to use the numpy.sign() method for 2D arrays.

# Import numpy
import numpy as np
# Create 2D array using np.array
x = np.array([[-7, -3.4 , 1.2 + 1j], [2, 3 + 1j, -9.5]])
# Find the sign of each element in the array
# Use np.sign()
result = np.sign(x)

print(result)

### Explanation

• Line 2: We import the numpy library.
• Lines 4: We create a 2D array called x consisting of complex and non-complex elements.
• Line 7: We use the np.sign() method to compute the sign of each number of the x input array.
• Line 9: We print out the result.

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python3
numpy
python

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