A.King
0
Let's say we have an array a = [5, 2, 3, 8, 4, 1, 9]
I want to choose a few elements (without replacement) so that the relative order of the chosen elements will be the same as in an input array.
Using the random.choice with shuffle=False doesn't seem to do this.
a = [5, 2, 3, 8, 4, 1, 9]
rng = np.random.default_rng(42)
rng.choice(a, 4, replace=False, shuffle=False)
Output:
array([9, 5, 1, 8])
I want to see:
array([5, 8, 1, 9])
What's the simplest way to achieve this result?
One method I can think of is to randomly choose indices first, and then filter the original list according to this set of indices:
import random
a = [5, 2, 3, 8, 4, 1, 9]
idx = set(random.sample(range(len(a)), k=4))
output = [x for i, x in enumerate(a) if i in idx]
print(output) # [5, 2, 3, 1]
Using numpy under the same idea,
import numpy as np
from numpy.random import default_rng
a = np.array([5, 2, 3, 8, 4, 1, 9])
output = a[sorted(default_rng().choice(range(len(a)), size=4, replace=False))]
print(output) # [5 3 4 9]
Sample k random elements and sort the result according to the index in lst:
import random
def select_k_sorted(lst, k):
return sorted(random.sample(lst, k), key=lst.index)