What is the expectation maximization algorithm?
2013-11-17 23:39
302 查看
http://www.nature.com/nbt/journal/v26/n8/full/nbt1406.html
对于最大似然概率的推导可以参考本系列中的文章
也就是说要求的是抛硬币A是正面的概率p(A), 和抛硬币B是正面的概率p(B)
一共做了五组实验,其中三组是抛10次A,正面的次数。
对于这三组的现象的概率是 p(data|A)=p(h|A)*(1-p(h|a))...p(h|A)
两边去对数,让其导数为0, 就可以计算出p(h|A)
为什么要让概率最大?这是因为这三组实验的结果就是在p(h|A)的概率分布下最有可能出现的现象。
对于EM:
也是同样做了5组抛硬币的实验,但是对于每组实验不知道是用A或者B做的实验,目的还是求p(A), p(B)
1. 设初始概率为p(A)=0.6, p(B) = 0.5
2. E步,当第一组是用A实验,可以求出第一组现象出现的概率,再求出用B做实验,第一组现象出现的概率,然后就可以计算出第一组数据用A或者B做实验的概率,0.6^5*(1-0.6)^5/0.5^10 = 0.445/0.55
然后可以算出A和B出现正面的期望Exception
3. M步,根据E步算出的Exception计算出p(A),p(B), 根据的是最大(Maximization)期望对数似然
对于最大似然概率的推导可以参考本系列中的文章
也就是说要求的是抛硬币A是正面的概率p(A), 和抛硬币B是正面的概率p(B)
一共做了五组实验,其中三组是抛10次A,正面的次数。
对于这三组的现象的概率是 p(data|A)=p(h|A)*(1-p(h|a))...p(h|A)
两边去对数,让其导数为0, 就可以计算出p(h|A)
为什么要让概率最大?这是因为这三组实验的结果就是在p(h|A)的概率分布下最有可能出现的现象。
对于EM:
也是同样做了5组抛硬币的实验,但是对于每组实验不知道是用A或者B做的实验,目的还是求p(A), p(B)
1. 设初始概率为p(A)=0.6, p(B) = 0.5
2. E步,当第一组是用A实验,可以求出第一组现象出现的概率,再求出用B做实验,第一组现象出现的概率,然后就可以计算出第一组数据用A或者B做实验的概率,0.6^5*(1-0.6)^5/0.5^10 = 0.445/0.55
然后可以算出A和B出现正面的期望Exception
3. M步,根据E步算出的Exception计算出p(A),p(B), 根据的是最大(Maximization)期望对数似然
相关文章推荐
- EM算法(Expectation - Maximization)通俗实例(What is the expectation maximization algorithm?)
- What is the expectation maximization algorithm?
- What is the difference between a Generative and Discriminative Algorithm?
- What is the Big O analysis of this algorithm?(Stackoverflow)
- What is the best free memory leak detector for a C/C++ program and its plug-in DLLs
- UVa10107 What is the Median?
- What is the working set, commit, and private working set memory size?
- [zt]---What is the data in the VSTS load test results store
- What is the difference between data mining and machine learning?
- VMware tools 共享文件夹安装时:What is the location of the directory of C header files (install VMware tools)
- what is the purpose of channel coding?(信道编码的作用?)
- 18 What is the __dict__.__dict__attribute of a Python class
- What is the difference between WinRT, UWP and WPF?
- uva 10056 - What is the Probability ?(概率)
- What is the difference between a binary tree, a binary search tree, a B tree and a B+ tree?
- What is the basic difference between NSTimer, NSTask, NSThread and NSRunloop?
- So, IT workers, what is the most disgusting work area you had to work on.
- what is the use of truncate command
- uva 10107 - What is the Median?
- A man speaks truth 3 out of 4 times. He throws a die and reports it to be a 6. What is the probabili