I am trying to split an array into three new arrays using inequalities.

This will give you an idea of what I am trying to achieve:

measurement = [1, 5, 10, 13, 40, 43, 60]

for x in measurement:
    if 0 < x < 6:
        small = measurement
    elif 6 < x < 15:
        medium = measurement
    else
        large = measurement

Intended Output:

small = [1, 5]
medium = [10, 13]
large = [40, 43, 60]

CodePudding user response：

If your array is sorted, you can do :

measurement = [1, 5, 10, 13, 40, 43, 60]
one_third = len(measurement) // 3
two_third = (2 * len(measurement)) // 3

small = measurement[:one_third]
medium = measurement[one_third : two_thirds]
large = measurement[two_thirds:]

You could easily generalize to any number of split with a loop. Not sure if you wanted explicitly those inequalities or just split with the array in three. If its the first one, my answer is not right

CodePudding user response：

You can use numpy:

arr = np.array(measurement)     
small = arr[(arr>0)&(arr<6)]    # array([1, 5])
medium = arr[(arr>6)&(arr<15)]  # array([10, 13])
large = arr[(arr>15)]           # array([40, 43, 60])

You can also use dictionary:

d = {'small':[], 'medium':[], 'large':[]}
for x in measurement:
    if 0 < x < 6:
        d['small'].append(x)
    elif 6 < x < 15:
        d['medium'].append(x)
    else:
        d['large'].append(x)

Output:

{'small': [1, 5], 'medium': [10, 13], 'large': [40, 43, 60]}

CodePudding user response：

With the bisect module you can do something along these lines:

from bisect import bisect
breaks=[0,6,15,float('inf')]
buckets={}

m = [1, 5, 10, 13, 40, 43, 60]

for e in m:
    buckets.setdefault(breaks[bisect(breaks, e)], []).append(e)

You then have a dict of lists matching what you are looking for:

>>> buckets
{6: [1, 5], 15: [10, 13], inf: [40, 43, 60]}

You can also form tuples of your break points and list that will become a dict to form the sub lists:

m = [1, 5, 10, 13, 40, 43, 60]
buckets=[('small',[]), ('medium',[]), ('large',[]), ('other',[])]

breaks=[(0,6),(6,15),(15,float('inf'))]

for x in m:
    buckets[
        next((i for i,t in enumerate(breaks) if t[0]<=x<t[1]), -1)
           ][1].append(x)

>>> dict(buckets)
{'small': [1, 5], 'medium': [10, 13], 'large': [40, 43, 60], 'other': []}