问题描述
我有一个包含这些归一化值的列表
list_a = [0.25,0.25,0.25]
现在,我想将一个条目的值更改为另一个数字,例如0.75
。此数字是固定的,不应再更改。
list_a_changed = [0.25,0.75,0.25]
要仍然确保列表中所有值的总和为1
,其余值必须为0.0833
。所以我的清单必须是:
list_a_normalized = [0.083,0.083,0.083]
这很容易弄清楚所有值在初始列表中是否共享相同的百分比。我可以只做1 - 0.75 = 0.25
,然后将0.25
除以其余数字,因为它们都占总数的百分比。
value_change = 0.75
remaining_value = 1 - value_change
divided_remaining_value = remaining_value / (len(list_a_changed) - 1)
list_a_normalized = [divided_remaining_value,divided_remaining_value,value_change,divided_remaining_value ]
但是如果原始列表如下所示,您将如何处理?
list_b = [0.25,0.45,0.20,0.10]
然后将一个值更改为0.05
list_b_changed = [0.25,0.05,0.10]
您将如何计算其他数字的值,以便它们各自保留其余0.95
的适当部分?
解决方法
您可以
- 计算
remaining
- 计算未更改值的总数,以获取未更改值的相对比例
- 将它们的值乘以剩余值,以将其考虑在内,然后除以相对总数,使它们与总数成比例
def normalize(values,index_not_change):
remaining = 1 - values[index_not_change]
total_except_remaining = sum(values) - values[index_not_change]
return [(value * remaining / total_except_remaining if idx != index_not_change else value)
for idx,value in enumerate(values)]
print(normalize([0.25,0.25,0.75,0.25],2)) # [0.0833333333,0.0833333333,0.0833333333]
print(normalize([0.25,0.45,0.05,0.10],2)) # [0.296875,0.534375,0.11875000000000001]
要了解total_except_remaining
的目的,没有它就是
normalize([0.25,2) -> [0.0625,0.0625,0.0625]
因为您已经计算出剩余(0.25
)的四分之一,但是加上相对和为0.75
而不是1的事实,您将更新为它们的实际比例
您也可以使用相同的方法修改
def normalize(values,position,new_value):
values[position] = new_value
remaining = 1 - new_value
total_except_remaining = sum(values) - new_value
return [(value * remaining / total_except_remaining if idx != position else value)
for idx,2,0.75))
,
使用change_normalized
项并使列表规范化:re_normalize
通过乘以正确的因子(这是一个与未更改项目的总和之比)来使列表规范化:
def change_normalized(lst,index,value):
def touch(lst,value):
lst[index] = value
def re_normalize(lst,value):
multiply_factor = (1 - value) / (sum(lst) - value)
for j in range(len(lst)):
if i == j:
continue
lst[j] *= multiply_factor
touch(lst,i,value)
re_normalize(lst,value)
i = 2
value = 0.05
list_b = [0.25,0.20,0.10]
# Change item at index to value and keep list normalized
change_normalized(list_b,value)
# 1.0
print(sum(list_b))
此代码可以缩小为:
def change_normalized(lst,value):
lst[index] = value
multiply_factor = (1 - value) / (sum(lst) - value)
lst[:] = [multiply_factor * x if i != j else x for j,x in enumerate(lst)