Assign array values to contiguous intervals-CodePudding

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?

CodePudding user response：

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)