# Today I learned

On the AI/Fastai front:

- If
`x`

is a`torch.Tensor`

and`x.shape`

is`torch.Size([4, 3, 5])`

, it means`x`

contains 4 2D matrices with 3 rows and 5 columns. Also,`x`

is 3D matrix, the technical term for which would be a rank-3 tensor. - When images are represented using PyTorch
`tensor`

s, the first dimension corresponds to the number of channels in it. (For e.g., an RGB image will contain 3 channels and, therefore, the first element in the tensor`shape`

will be`3`

.)- Matplotlib’s
`imshow`

function expects number of channels at the end and you can modify a`tensor`

to that by applying the`permute`

function.

- Matplotlib’s