Extract values from a list using a numpy range of indices between every two numbers

Question

I want to extract a range of indices contained in the 'ranges' list from the 'nums' array.

For example:

ranges=np.arange(10, 100, 10).tolist() 
#[10, 20, 30, 40, 50, 60, 70, 80, 90]

nums=np.arange(10, 1000, 5.5)

Here, I want to extract indices 10 to 20, and then 20 to 30 and so on until indices 80 to 90 specified in the 'ranges' list from the 'nums' array. I'm not sure how to cycle between every two numbers through the 'ranges' list.

If I just had to extract 2-3 ranges of indices, I would just hard code the indices and slice-

idx1 = nums[10:21]
idx2 = nums[20:31]
idx3 = nums[30:41]

But this gets tedious to do for various combinations of ranges, especially in my original dataset with almost 100 ranges of indices to extract.

Appreciate any help on this.

Looks like it is just reshaping what you aim to do: nums[10:].reshape(-1,10). — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Jul 9, 2020 at 16:02

avysk · Accepted Answer · 2020-07-09 16:11:55Z

2

Something like this?

>>> ranges = [10, 20, 35, 42]
>>> for start, end in zip(ranges[:-1], ranges[1:]):
...     print(start, end)
...
10 20
20 35
35 42

(Of course, do your extraction in place of print)

answered Jul 9, 2020 at 16:11

avysk

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Red · Accepted Answer · 2020-07-09 16:03:48Z

2

You can use a for loop with a chosen step:

idxs = []

for n in range(10, 1000, 10):
    idx.append(nums[n:n+11])

answered Jul 9, 2020 at 16:03

Red

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Comments

Raph the raph · Accepted Answer · 2020-07-09 16:12:12Z

1

This should do it :

dic={}
for i in np.transpose([ranges[:-1],ranges[1:]]):
     dic[str(i[0])+"-"+str(i[1])]=nums[i[0]:i[1]]
print(dic)

answered Jul 9, 2020 at 16:12

Raph the raph

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