How To Normalize Array Between 1 and 10?

Question

I have a numpy array with the following integer numbers:

[10 30 16 18 24 18 30 30 21 7 15 14 24 27 14 16 30 12 18]

I want to normalize them to a range between 1 and 10.

I know that the general formula to normalize arrays is:

But how am I supposed to scale them between 1 and 10?

Question: What is the simplest/fastest way to normalize this array to values between 1 and 10?

Possible duplicate https://stackoverflow.com/questions/21030391/how-to-normalize-an-array-in-numpy?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa — Naor Tedgi, May 12 '18 at 10:26
@NaorTedgi that's not a good dupe: OP already knows how to normalize an array. — Andras Deak -- Слава Україні, May 12 '18 at 10:57

Andras Deak -- Слава Україні · Accepted Answer · 2018-05-12T10:45:08.743

8

Your range is actually 9 long: from 1 to 10. If you multiply the normalized array by 9 you get values from 0 to 9, which you need to shift back by 1:

start = 1
end = 10
width = end - start
res = (arr - arr.min())/(arr.max() - arr.min()) * width + start

Note that the denominator here has a numpy built-in named arr.ptp():

res = (arr - arr.min())/arr.ptp() * width + start

edited May 12 '18 at 10:45

answered May 12 '18 at 10:39

1 Answers1