diff --git a/content/pytorch/concepts/tensor-operations/terms/sgn/sgn.md b/content/pytorch/concepts/tensor-operations/terms/sgn/sgn.md new file mode 100644 index 00000000000..aace812a033 --- /dev/null +++ b/content/pytorch/concepts/tensor-operations/terms/sgn/sgn.md @@ -0,0 +1,101 @@ +--- +Title: '.sgn()' +Description: 'Computes the sign of each element in the input tensor, returning a tensor with the same shape.' +Subjects: + - 'Computer Science' + - 'Data Science' +Tags: + - 'Deep Learning' + - 'Methods' + - 'PyTorch' + - 'Tensor' +CatalogContent: + - 'intro-to-py-torch-and-neural-networks' + - 'paths/data-science' +--- + +The **`.sgn()`** function computes the sign of each element in the input [tensor](https://www.codecademy.com/resources/docs/pytorch/tensors), applied element-wise. For real-valued tensors, it returns -1 for negative values, 0 for zero, and 1 for positive values. For complex-valued tensors, it returns the complex sign (the tensor divided by its absolute value), which gives the unit vector in the direction of each complex number. + +## Syntax + +```pseudo +torch.sgn(input, *, out=None) → Tensor +``` + +**Parameters:** + +- `input` (Tensor): The input tensor (can be real or complex). +- `out` (Tensor, optional): Optional output tensor to store the result. + +**Return value:** + +A tensor with the same shape as `input`, containing the sign of each element. + +## Example 1: Using `.sgn()` with a Real-Valued Tensor + +In this example, `.sgn()` computes the sign of each element in a real-valued tensor: + +```py +import torch + +# Create a tensor with positive, negative, and zero values +x = torch.tensor([-5.0, -2.5, 0.0, 2.5, 5.0]) + +# Compute the sign +result = torch.sgn(x) + +print(result) +``` + +The output of this code is: + +```shell +tensor([-1., -1., 0., 1., 1.]) +``` + +## Example 2: Applying `.sgn()` element-wise to a 2D tensor + +In this example, `.sgn()` is applied to a 2D tensor: + +```py +import torch + +# Create a 2x3 tensor +matrix = torch.tensor([[-3.0, -1.0, 0.0], [1.0, 2.0, 3.0]]) + +# Compute the sign +result = torch.sgn(matrix) + +print(result) +``` + +The output of this code is: + +```shell +tensor([[-1., -1., 0.], + [ 1., 1., 1.]]) +``` + +## Example 3: Using `.sgn()` with Complex Numbers + +For complex-valued tensors, `.sgn()` returns the complex sign, which is the unit vector in the direction of each complex number (computed as `x / |x|`): + +```py +import torch + +# Create a tensor with complex numbers +z = torch.tensor([1+2j, -1+2j, 3-4j]) + +# Compute the complex sign +result = torch.sgn(z) + +print(result) +``` + +The output of this code is: + +```shell +tensor([0.4472+0.8944j, -0.4472+0.8944j, 0.6000-0.8000j]) +``` + +In this example, each result has a magnitude of 1 (a unit vector), pointing in the direction of the original complex number.