在Python中如何找到列表的中值?列表可以是任意大小的，并且数字不保证是任何特定的顺序。
如果列表包含偶数个元素，则函数应返回中间两个元素的平均值。
以下是一些例子(为了便于展示，进行了排序):
median([1]) == 1
median([1, 1]) == 1
median([1, 1, 2, 4]) == 1.5
median([0, 2, 5, 6, 8, 9, 9]) == 6
median([0, 0, 0, 0, 4, 4, 6, 8]) == 2
当前回答
实现它:
def median(numbers):
"""
Calculate median of a list numbers.
:param numbers: the numbers to be calculated.
:return: median value of numbers.
>>> median([1, 3, 3, 6, 7, 8, 9])
6
>>> median([1, 2, 3, 4, 5, 6, 8, 9])
4.5
>>> import statistics
>>> import random
>>> numbers = random.sample(range(-50, 50), k=100)
>>> statistics.median(numbers) == median(numbers)
True
"""
numbers = sorted(numbers)
mid_index = len(numbers) // 2
return (
(numbers[mid_index] + numbers[mid_index - 1]) / 2 if mid_index % 2 == 0
else numbers[mid_index]
)
if __name__ == "__main__":
from doctest import testmod
testmod()
来源
其他回答
我为一组数字定义了一个中值函数
def median(numbers):
return (sorted(numbers)[int(round((len(numbers) - 1) / 2.0))] + sorted(numbers)[int(round((len(numbers) - 1) // 2.0))]) / 2.0
实现它:
def median(numbers):
"""
Calculate median of a list numbers.
:param numbers: the numbers to be calculated.
:return: median value of numbers.
>>> median([1, 3, 3, 6, 7, 8, 9])
6
>>> median([1, 2, 3, 4, 5, 6, 8, 9])
4.5
>>> import statistics
>>> import random
>>> numbers = random.sample(range(-50, 50), k=100)
>>> statistics.median(numbers) == median(numbers)
True
"""
numbers = sorted(numbers)
mid_index = len(numbers) // 2
return (
(numbers[mid_index] + numbers[mid_index - 1]) / 2 if mid_index % 2 == 0
else numbers[mid_index]
)
if __name__ == "__main__":
from doctest import testmod
testmod()
来源
更普遍的中位数(和百分位数)方法是:
def get_percentile(data, percentile):
# Get the number of observations
cnt=len(data)
# Sort the list
data=sorted(data)
# Determine the split point
i=(cnt-1)*percentile
# Find the `floor` of the split point
diff=i-int(i)
# Return the weighted average of the value above and below the split point
return data[int(i)]*(1-diff)+data[int(i)+1]*(diff)
# Data
data=[1,2,3,4,5]
# For the median
print(get_percentile(data=data, percentile=.50))
# > 3
print(get_percentile(data=data, percentile=.75))
# > 4
# Note the weighted average difference when an int is not returned by the percentile
print(get_percentile(data=data, percentile=.51))
# > 3.04
简单地说，创建一个中值函数，参数为数字列表，并调用该函数。
def median(l):
l = sorted(l)
lent = len(l)
if (lent % 2) == 0:
m = int(lent / 2)
result = l[m]
else:
m = int(float(lent / 2) - 0.5)
result = l[m]
return result
这很简单;
def median(alist):
#to find median you will have to sort the list first
sList = sorted(alist)
first = 0
last = len(sList)-1
midpoint = (first + last)//2
return midpoint
你可以这样使用返回值median = median(anyList)
