Understanding numpy shape

Question

I'm newbie with Python and also with Numpy.

I have this code:

one_array.shape

When I run it, I get this output:

(20, 48, 240, 240)

one_array is a Numpy Array that has 20 images.

What do mean the other three numbers in shape output (48, 240, 240)?

I suspect you have 20, 3 band (Red, Green Blue) images with a size of 240x240 pixels (originally) — NaN, Dec 19 '19 at 14:10
Does this answer your question? [what does numpy ndarray shape do?](https://stackoverflow.com/questions/47564495/what-does-numpy-ndarray-shape-do) — Georgy, Dec 19 '19 at 15:13

David · Accepted Answer · 2019-12-19T14:23:03.313

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Your array consist of 20 images, each of them is the size 48X240X240. Which is odd, I would expect that it will be something like 240X240X3 but for some reason you have way more channels (referring to RGB). ]

So the shape function return the size of dimension along each axis (the current shape of the entire array), so in your case there is (20, 48, 240, 240)

Edit:

As the user said, each image consist of 48 NITFY images of 1 channel which explain the output of shape

edited Dec 19 '19 at 14:23

answered Dec 19 '19 at 14:12

David

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Thanks for your answer. I think is: 20 elements in the array. Each of these elements are a NIFTY image. Each of these NITFY images are: 48 images of 240x240. – VansFannel Dec 19 '19 at 14:19
@VansFannel Thanks for the acceptance, I added your comment to my answer in that it will be clearer to one reading the answer – David Dec 19 '19 at 14:23
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You are welcome. I have used the program MRIcron to open a T1.nii.gz and check that it has 48 images, 240x240 each of them. – VansFannel Dec 19 '19 at 14:33

score 0 · Answer 2 · answered Dec 19 '19 at 14:08

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Imagine your Numpy Array as a Vector that can be in one dimension, but in your case it looks like it is in dimension 4. (20, 4, 240, 240) means a big matrix composed of 20 x 4 x 240 x 240 elements.

answered Dec 19 '19 at 14:08

Phoenixo

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score 0 · Answer 3 · answered Dec 19 '19 at 14:09

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one_array.shape == (20, 48, 240, 240) means that one_array is a 4-dimensional array with 20*48*240*240 or 55296000 elements.

answered Dec 19 '19 at 14:09

9mat

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score 0 · Answer 4 · answered Dec 19 '19 at 14:10

You are right, you can think of one_array as an array with 20 elements, in which is element in another array with shape (48, 240, 240). However, usually is it better to think that one_array is a 4 dimensional array, that has a total of 20x48x240x240 = 55296000 elements.

Understanding numpy shape

4 Answers4