# Subtract constant value from tensor

**URL:** <https://discuss.pytorch.org/t/subtract-constant-value-from-tensor/136376>\
**Category:** Uncategorized\
**Created:** [November 9, 2021, 9:14am UTC](https://discuss.pytorch.org/t/subtract-constant-value-from-tensor/136376 "2021-11-09T09:14:21Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cbd](https://discuss.pytorch.org/letter_avatar_proxy/v4/letter/c/13edae/32.png) [@cbd](https://discuss.pytorch.org/u/cbd)\
**Post date:** [November 9, 2021, 9:14am UTC](https://discuss.pytorch.org/t/subtract-constant-value-from-tensor/136376/1 "2021-11-09T09:14:21Z")

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“tensor\_a” is of size (1,3,4,4) and “tensor\_b” is of size(3).

I want to subtract constant value from each channel. For below code, i want to subtract constant value 1 from 1st channel, 2 from 2nd channel and 3 from 3rd channel.

```auto
import torch

a=torch.Tensor([[[[1., 2., 3., 4.],
          [5., 6., 7., 8.],
          [9., 10., 11., 12.],
          [13., 14., 15., 16.]],

         [[17., 18., 19., 20.],
          [21., 22., 23., 24.],
          [25., 26., 27., 28.],
          [29., 30., 31., 32.]],

         [[33., 34., 35., 36.],
          [37., 38., 39., 40.],
          [41., 42., 43., 44.],
          [45., 46., 47., 48.]]]])
b=torch.tensor([1., 2., 3.])
print("a shape is ",a.shape)
print("b shape is ",b.shape)
```

---

<div class="post-metadata">

**Author:** ![lupus83](https://discuss.pytorch.org/user_avatar/discuss.pytorch.org/lupus83/32/43687_2.png) [@lupus83](https://discuss.pytorch.org/u/lupus83)\
**Post date:** [November 9, 2021, 1:11pm UTC](https://discuss.pytorch.org/t/subtract-constant-value-from-tensor/136376/2 "2021-11-09T13:11:47Z")

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This should do the trick:

```auto
b = b.view(1, *b.size(), 1, 1).expand_as(a)

```