Re: [Numpy-discussion] Find n closest values

On So, 2014-06-22 at 17:16 +0200, Nicolas P. Rougier wrote:

Thanks for the answer. I was secretly hoping for some kind of hardly-known numpy function that would make things faster auto-magically...

I doubt it is faster, but if you got scipy anyway, using KDTree may be pretty idiomatic. - Sebastian

Nicolas

On 22 Jun 2014, at 10:30, Eelco Hoogendoorn wrote:

...

Perhaps you could simplify some statements, but at least the algorithmic complexity is fine, and everything is vectorized, so I doubt you will get huge gains.

You could take a look at the functions in scipy.spatial, and see how they perform for your problem parameters.

On Sun, Jun 22, 2014 at 10:22 AM, Nicolas P. Rougier wrote:

Hi,

I have an array L with regular spaced values between 0 and width. I have a (sorted) array I with irregular spaced values between 0 and width.

I would like to find the closest value in I for any value in L.

Currently, I'm using the following script but I wonder if I missed an obvious (and faster) solution:

import numpy as np

def find_closest(A, target): idx = A.searchsorted(target) idx = np.clip(idx, 1, len(A) - 1) left = A[idx - 1] right = A[idx] idx -= target - left < right - target return idx

n, width = 256, 100.0

# 10 random sorted values in [0,width] I = np.sort(np.random.randint(0,width,10))

# n regular spaced values in [0,width] L = np.linspace(0, width, n)

print I[find_closest(I,L)]

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