PyTorch .imag

The .imag property in PyTorch returns the imaginary part of each element in a complex tensor. For complex numbers, it returns the coefficient of the imaginary unit (j), and for real numbers, it returns zero. This method is essential for complex number analysis, signal processing, and mathematical operations involving complex tensors.

Syntax

tensor.imag

Return value:

The .imag property returns a new tensor containing the imaginary parts of each element in the input tensor. The output tensor has the same shape as the input tensor but contains only real values.

Example 1

The following example demonstrates how to use the .imag property to extract imaginary parts from a complex tensor:

import torch

# Create a complex tensor
complex_tensor = torch.tensor([[1 + 2j, 3 - 4j], [5 + 0j, -2 + 1j]])

# Extract the imaginary parts
imaginary_parts = complex_tensor.imag

print("Original Complex Tensor:")
print(complex_tensor)

print("\nImaginary Parts:")
print(imaginary_parts)

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This example produces the following output:

Original Complex Tensor:
tensor([[1.+2.j, 3.-4.j],
        [5.+0.j, -2.+1.j]])

Imaginary Parts:
tensor([[ 2., -4.],
        [ 0.,  1.]])

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In this example:

• 1 + 2j → imaginary part is 2.0
• 3 - 4j → imaginary part is -4.0
• 5 + 0j → imaginary part is 0.0 (0.0 is also a real number)
• -2 + 1j → imaginary part is 1.0

Example 2

Run the following code to see how .imag works with different types of complex numbers:

import torch

# Create tensors with different complex numbers
complex_numbers = torch.tensor([1 + 3j, 2 - 5j, 4 + 0j, -1 - 2j])

# Extract imaginary parts
imag_parts = complex_numbers.imag

print("Complex numbers:", complex_numbers)
print("Imaginary parts:", imag_parts)

# Create a 2D complex tensor
matrix_2d = torch.tensor([[1 + 1j, 2 - 2j], [3 + 3j, 4 - 4j]])
print("\n2D complex matrix:")
print(matrix_2d)
print("\nImaginary parts of 2D matrix:")
print(matrix_2d.imag)

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The output of this code is:

Complex numbers: tensor([ 1.+3.j,  2.-5.j,  4.+0.j, -1.-2.j])
Imaginary parts: tensor([ 3., -5.,  0., -2.])

2D complex matrix:
tensor([[1.+1.j, 2.-2.j],
        [3.+3.j, 4.-4.j]])

Imaginary parts of 2D matrix:
tensor([[ 1., -2.],
        [ 3., -4.]])

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The .imag property is useful for:

• Separating real and imaginary components for analysis
• Performing operations specifically on imaginary parts of data
• Visualizing imaginary components of complex signals
• Implementing algorithms that require distinct handling of real and imaginary values