Python统计模块中的 median_low()函数

中位数通常被称为中心位置的稳健度量，受数据中异常值的影响较小。

Python中的统计模块允许三个选项来处理数据集中的中值/中间元素，它们是median(), median_low() and median_high() 。

低中位数始终是数据集的成员。当数据点数为奇数时，返回中间值。如果是偶数，则返回两个中间值中较小的一个。让我们看看median_low()是如何工作的。

Syntax : median_low( [data-set] )

Parameters :
[data-set] : Takes in a list, tuple or an interable set of numeric data.

Returntype : Returns the low median of numeric data. Low median is a member of actual data-set.

Exceptions : StatisticsError is raised when data-set is empty.

编程需要懂一点英语

代码#1：工作

# Python code to demonstrate the 
# working of median_low()
  
# importing the statistics module
import statistics
  
# simple list of a set of integers
set1 = [1, 3, 3, 4, 5, 7]
  
# Note: low median will always be
#        a member of the data-set.
  
# Print low median of the data-set
print("Low median of the data-set is % s " 
        % (statistics.median_low(set1)))

输出：

Low median of the data-set is 3

代码#2：使用 median_low() 和中位数来区分它们。

# Python code to demonstrate the
# working of median_low()
  
# importing the statistics module
import statistics
  
# simple list of a set of integers
set1 = [1, 3, 3, 4, 5, 7]
  
# Print median of the data-set
  
# Median value may or may not
# lie within the data-set
print("Median of the set is % s" 
      % (statistics.median(set1)))
  
# Print low median of the data-set
print("Low Median of the set is % s " 
       % (statistics.median_low(set1)))

输出：

Median of the set is 3.5
Low Median of the set is 3

代码 #3：在不同范围的数据集上使用 median_low()

# Python code to demonstrate the
# working of median_low()
  
# importing statistics module
from statistics import median_low
  
# Importing fractions module as fr
from fractions import Fraction as fr
  
# tuple of positive integer numbers
data1 = (2, 3, 4, 5, 7, 9, 11)
  
# tuple of a set of floating-point values
data2 = (2.4, 5.1, 6.7, 8.9)
  
# tuple of a set of fractional numbers
data3 = (fr(1, 2), fr(44, 12),
         fr(10, 3), fr(2, 3))
  
# tuple of a set of negative integers
data4 = (-5, -1, -12, -19, -3)
  
# tuple of set of positive
# and negative integers
data5 = (-1, -2, -3, -4, 4, 3, 2, 1)
  
# Print low_median() of given data-sets
print("Low Median of data-set 1 is % s" % (median_low(data1)))
print("Low Median of data-set 2 is % s" % (median_low(data2)))
print("Low Median of data-set 3 is % s" % (median_low(data3)))
print("Low Median of data-set 4 is % s" % (median_low(data4)))
print("Low Median of data-set 5 is % s" % (median_low(data5)))

输出：

Low Median of data-set 1 is 5
Low Median of data-set 2 is 5.1
Low Median of data-set 3 is 2/3
Low Median of data-set 4 is -5
Low Median of data-set 5 is -1

代码#4：引发统计错误

# Python code to demonstrate
# StatisticsError of median_low()
  
# importing the statistics module
from statistics import median_low
  
# creating an empty data-set
empty = []
  
# will raise StatisticsError
print(median_low(empty))

输出：

Traceback (most recent call last):
  File "/home/5f3e758236f872d014f9d741743c30a4.py", line 10, in 
    print(median_low(empty))
  File "/usr/lib/python3.5/statistics.py", line 376, in median_low
    raise StatisticsError("no median for empty data")
statistics.StatisticsError: no median for empty data

应用：
当数据是离散的并且更喜欢中位数作为数据中的实际点而不是外推点时，使用median_low() 。