Assign array values to contiguous intervals

Question

I have a levels array

#                  0    1    2    3   4
levels = np.array(( 0.2, 0.4, 0.6, 0.8 ))

and a values array, e.g.,

np.random.seed(20230204)
values = np.random.rand(5)

and eventually a SLOW function

def map_into_levels(values, levels):
    result = []
    for n in np.asarray(values):
        for r, level in enumerate(levels):
            if n <= level:
                break
        else:
            r += 1
        result.append(r)
    return result

so that I have

In [153]: np.random.seed(20220204)
     ...: values = np.random.rand(6)
     ...: levels = np.array(( 0.2, 0.4, 0.6, 0.8 ))
     ...: result = map_into_levels(values, levels)
     ...: print(levels)
     ...: print(values)
     ...: print(result)
[0.2 0.4 0.6 0.8]
[0.00621839 0.23945242 0.87124946 0.56328486 0.5477085  0.88745812]
[0, 1, 4, 2, 2, 4]

In [154]:

Could you please point me towards a Numpy primitive that helps me to speed up the operations?

I'm not particularly happy with my title… I encourage you to edit it. — gboffi
– gboffi, Commented Feb 4, 2023 at 19:49

akuiper · Accepted Answer · 2023-02-04 20:03:43Z

1

You need np.searchsorted assuming levels is sorted already. It find indices where elements should be inserted to maintain order:

np.searchsorted(levels, values)
# array([0, 1, 4, 2, 2, 4], dtype=int32)

answered Feb 4, 2023 at 20:03

akuiper

216k33 gold badges363 silver badges380 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Assign array values to contiguous intervals

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related