[英]Possible to calculate a double sum in python using list comprehensions to replace both for-loops?
[英]Calculate variance of an array using for-loops, Python
我剛剛開始學習 Python,現在我必須使用 for 循環計算數組中的均值和方差。
目前,我得到一個不正確的方差值,我不知道為什么。
numbers = [7, 16, 0.3, 0, 15, -4, 5, 3, 15]
sum = 0
for value in range(0, len(numbers)):
sum = sum + numbers[value]
mean_value = sum / len(numbers)
print(mean_value)
n = len(numbers)
sum_squares = 0
for value in range(0, len(numbers)):
sum_squares = sum_squares + (value - mean_value) ** 2
var_value = sum_squares / n
print(var_value)
根據在線計算器,我應該得到方差 = 55.035,我得到的方差為 12.267
我將不勝感激任何幫助。
ķ
編輯:我剛剛意識到將第二部分更改為此有效:
for value in numbers:
sum_squares = sum_squares + ((value - mean_value) ** 2)
var_value = sum_squares / n
不確定“for value in numbers:”和“for value in range(0, len(numbers)):”之間的確切區別是什么,但這是有幫助的。
方差除以 (n-1)
numbers = [7, 16, 0.3, 0, 15, -4, 5, 3, 15]
sum = 0
count = 0
sum_squares = 0
for value in numbers:
sum = sum + value
count = count + 1
mean_value = (sum / count)
for value in numbers:
sum_squares = sum_squares + ((value - mean_value)** 2)
var_value = sum_squares / (count-1)
print (mean_value)
print (var_value)
出去:
6.366666666666666
55.035
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.