dbliss dbliss - 1 year ago 74
Python Question

Vectorizing a function that finds the nearest value in an array

I've written the following function:

import numpy as np

def _find_nearest(array, value):
"""Find the index in array whose element is nearest to value.

array : np.array
The array.

value : number
The value.

The index in array whose element is nearest to value.

if array.argmax() == array.size - 1 and value > array.max():
return array.size
return (np.abs(array - value)).argmin()

I'd like to vectorize this function, so that I can pass several values at once. That is, I'd like to have
be an array, and have
return, rather than a single index, the indices for each of the values in the submitted

Can anyone see a way to do this?

Answer Source

Inside the parent function, where both the value and the array are visible, you can use a lambda to enable the vectorization. I shall call the parent function main

def main():
    value = np.random.rand(10, 1)
    array = np.random.rand(100, 100)
    vec_nearest = lambda x: _find_nearest(array, x)

This will work on one array, and multiple values of vector. The return will be an array.

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